diff --git a/B06_Section/B06_Section_UI_Cross_Design.ts b/B06_Section/B06_Section_UI_Cross_Design.ts
index 19e1e8dbc..bf02980f5 100644
--- a/B06_Section/B06_Section_UI_Cross_Design.ts
+++ b/B06_Section/B06_Section_UI_Cross_Design.ts
@@ -113,6 +113,8 @@ export interface CrossDesignChange {
   /** 측구를 둘지 **사용자가 정한 선택**. `null` = 자동 판정.
    *  ⚠ 결과(`design.ditch_enabled` = 실제 섰나)와 **다른 값**이다(2026-09-09 정리). */
   ditch_choice: boolean | null;
+  /** 설계선 쉬프트(139-6) — 있으면 그 쪽 노견 확장만 바꾸는 변경(다른 칸은 안 씀). */
+  shoulder_extend?: { side: "left" | "right"; valueM: number };
 }
 
 /**
diff --git a/B06_Section/B06_Section_UI_Cross_Design_Pick.ts b/B06_Section/B06_Section_UI_Cross_Design_Pick.ts
index 15305baca..485538bb5 100644
--- a/B06_Section/B06_Section_UI_Cross_Design_Pick.ts
+++ b/B06_Section/B06_Section_UI_Cross_Design_Pick.ts
@@ -7,6 +7,7 @@
  * 선을 구조물 판정면 아래에 깐다. 고르면 그 조각을 강조하고 [+ − ⤢] 왼쪽에 치수를 적는다.
  * 구역 판정(`crossZoneAt` · 도로 · 절토 · 성토)은 설계선 쉬프트(139-6)도 쓴다.
  * 고름 상태는 페이지에 한 칸(측점 + 조각 번호) — 카드를 다시 그려도 되살아난다.
+ * 고른 조각의 쪽 노견을 [◀ ▶] 0.1 m 로 넓히고 좁힘(139-6 쉬프트 · 노폭 안쪽 금지 = 0 에서 멈춤).
  * ========================================================================== */
 
 import type { CrossDesign } from "./B06_Section_Api_Fetch";
@@ -238,6 +239,22 @@ const pointsOf = (element: Element): XY[] => {
     .filter((p) => p.length === 2 && p.every(Number.isFinite));
 };
 
+/** 설계선 쉬프트(139-6) — 쪽마다 노견 확장(m · ≥ 0). */
+export interface ShoulderShift {
+  valueOf: (side: CrossSide) => number;
+  set: (side: CrossSide, valueM: number) => void;
+}
+/** 쉬프트 걸음(m). */
+export const SHIFT_STEP_M = 0.1;
+
+/** 화면 ◀(−1) · ▶(+1) 한 걸음 → 그 쪽 노견 확장 새 값(0.1 m 눈금 · 0 아래 금지).
+ *  `kx` = 화면 x / offset 기울기(+offset = 좌 · 화면 왼쪽이면 kx < 0). */
+export function shiftedExtend(now: number, side: CrossSide, screenDir: -1 | 1, kx: number): number {
+  const offsetDelta = screenDir * Math.sign(kx) * SHIFT_STEP_M;
+  const outward = side === "left" ? offsetDelta : -offsetDelta;
+  return Math.max(0, Math.round((now + outward) * 10) / 10);
+}
+
 export interface DesignLinePick {
   pieces: DesignPiece[];
   /** 치수 칸 — 카드가 [+ − ⤢] 앞에 붙임 · 고름 없으면 숨김. */
@@ -255,6 +272,8 @@ export function attachDesignLinePick(input: {
   x: (offset: number) => number;
   toDisplayY: (elevation: number) => number;
   onPick: (index: number) => void;
+  /** 있으면 고른 조각 쪽 노견을 [◀ ▶] 로 옮김(139-6). */
+  shift?: ShoulderShift;
 }): DesignLinePick {
   const { layer, design, x, toDisplayY } = input;
   const x0 = x(0);
@@ -300,6 +319,28 @@ export function attachDesignLinePick(input: {
   const label = document.createElement("span");
   label.className = "b06-cross-card__line-dims";
   label.hidden = true;
+  const text = document.createElement("span");
+  label.append(text);
+  let side: CrossSide | null = null;
+  const { shift } = input;
+  if (shift) {
+    const button = (glyph: string, dir: -1 | 1, tip: string): HTMLButtonElement => {
+      const el = document.createElement("button");
+      el.type = "button";
+      el.className = "b06-cross-card__zoom-btn b06-cross-card__line-shift";
+      el.textContent = glyph;
+      el.title = tip;
+      el.addEventListener("click", (event) => {
+        event.stopPropagation();
+        if (side) shift.set(side, shiftedExtend(shift.valueOf(side), side, dir, kx));
+      });
+      return el;
+    };
+    label.append(
+      button("◀", -1, "고른 선 쪽 노견을 화면 왼쪽으로 0.1 m(노폭 안쪽은 못 감)"),
+      button("▶", 1, "고른 선 쪽 노견을 화면 오른쪽으로 0.1 m(노폭 안쪽은 못 감)"),
+    );
+  }
   return {
     pieces,
     label,
@@ -307,7 +348,11 @@ export function attachDesignLinePick(input: {
       const piece = index === null ? undefined : pieces[index];
       hits.forEach((hit, i) => hit.classList.toggle("is-active", !!piece && i === index));
       label.hidden = !piece;
-      label.textContent = piece ? pieceLabel(design, piece) : "";
+      side = piece ? pieceZone(design, piece).side : null;
+      const extend = side && shift ? shift.valueOf(side) : 0;
+      text.textContent = piece
+        ? pieceLabel(design, piece) + (extend > 0 ? ` · 노견 +${extend.toFixed(1)}m` : "")
+        : "";
     },
   };
 }
diff --git a/B06_Section/B06_Section_UI_Cross_View.ts b/B06_Section/B06_Section_UI_Cross_View.ts
index 19222df41..ab9d0181d 100644
--- a/B06_Section/B06_Section_UI_Cross_View.ts
+++ b/B06_Section/B06_Section_UI_Cross_View.ts
@@ -28,6 +28,7 @@ import {
   appendCrossDesignOverlay,
   appendPavementOverlay,
   appendRockBoundaryOverlay,
+  type CrossDesignChange,
   type RockBoundaryControl,
 } from "./B06_Section_UI_Cross_Design";
 import { appendCardFooter, appendCardHeader } from "./B06_Section_UI_Cross_Card_Chrome";
@@ -572,12 +573,24 @@ export function createCrossSectionCard(
       }
       raiseWalls(plotLayer); // 흙막이 · 옹벽 안을 지나는 다른 선 가림(66-5)
       // 보라 선 고름 — 가림 · 판정면 차례가 정해진 뒤(137-2).
+      const lineDesign = section.design;
       linePick = attachDesignLinePick({
         layer: plotLayer,
-        design: section.design,
+        design: lineDesign,
         x,
         toDisplayY,
         onPick: pickLine,
+        // 고른 선 쪽 노견 확장(139-6) — 카드 버튼과 같은 창구(세션 · 브라우저 재계산)
+        shift: onDesignChange
+          ? {
+              valueOf: (side) => lineDesign[`shoulder_extend_${side}_m`] ?? 0,
+              set: (side, valueM) =>
+                onDesignChange(section.chainage_m, {
+                  ...(lineDesign as unknown as CrossDesignChange),
+                  shoulder_extend: { side, valueM },
+                }),
+            }
+          : undefined,
       });
       setLineActive = linePick.setActive;
       setLineActive(pickedLineAt(section.station_id));
diff --git a/B06_Section/B06_Section_UI_Page_Design_Sync.ts b/B06_Section/B06_Section_UI_Page_Design_Sync.ts
index d63255462..b3cd18558 100644
--- a/B06_Section/B06_Section_UI_Page_Design_Sync.ts
+++ b/B06_Section/B06_Section_UI_Page_Design_Sync.ts
@@ -9,7 +9,7 @@
  *   - `applyPanelToAll`      : 표준 횡단면 설정 [전체 반영]
  * ========================================================================== */
 
-import { writeCrossDesignChoice } from "./B06_Section_Cross_Design_Session";
+import { writeCrossDesignChoice, writeShoulderExtend } from "./B06_Section_Cross_Design_Session";
 import { showToast } from "@ui/ui_template_elements";
 import { refreshCrossDesigns } from "./B06_Section_Cross_Refresh";
 import {
@@ -57,6 +57,15 @@ export function createDesignSync(ctx: DesignSyncContext): DesignSyncController {
     );
     if (!target) return;
 
+    // 설계선 쉬프트(139-6) — 그 쪽 노견 확장만 세션에 · 캐시에 바로 · 브라우저 재계산(같은 창구)
+    const shift = change.shoulder_extend;
+    if (shift) {
+      writeShoulderExtend(projectId, currentRouteId, chainageM, shift.side, shift.valueM);
+      if (target.design) target.design[`shoulder_extend_${shift.side}_m`] = shift.valueM;
+      await reconcileStaleDesigns({ force: true });
+      return;
+    }
+
     // (1) 즉시 로컬 반영: 선택 버튼만 갱신(숫자·설계선은 기존값 유지) → 해당 카드만 교체.
     if (target.design) {
       target.design = {
diff --git a/resources/tester/helper_139_6_line_shift.cjs b/resources/tester/helper_139_6_line_shift.cjs
new file mode 100644
index 000000000..97e9207ff
--- /dev/null
+++ b/resources/tester/helper_139_6_line_shift.cjs
@@ -0,0 +1,151 @@
+/* 139-6 고른 설계선 [◀ ▶] 노견 확장 헬퍼 — `_Cross_Design_Pick.attachDesignLinePick` 을 그 자리에서
+ * 트랜스파일해 흉내 DOM 으로 돌림. 짝 = `test_139_6_line_shift.py`.
+ */
+const fs = require("fs");
+const path = require("path");
+const ts = require(path.join(__dirname, "..", "..", "config", "node_modules", "typescript"));
+
+const ROOT = path.join(__dirname, "..", "..");
+const cache = new Map();
+
+class Node {
+  constructor(tag) {
+    this.tagName = tag;
+    this.children = [];
+    this.attrs = {};
+    this.listeners = {};
+    this.hidden = false;
+    this._text = "";
+    this._cls = new Set();
+    const self = this;
+    this.classList = {
+      add: (...n) => n.forEach((c) => self._cls.add(c)),
+      toggle: (c, on) => ((on ?? !self._cls.has(c)) ? self._cls.add(c) : self._cls.delete(c)),
+      contains: (c) => self._cls.has(c),
+    };
+  }
+  set className(v) {
+    this._cls = new Set(String(v).split(/\s+/).filter(Boolean));
+  }
+  set textContent(v) {
+    this._text = String(v);
+  }
+  get textContent() {
+    return this._text + this.children.map((c) => c.textContent).join("");
+  }
+  append(...kids) {
+    this.children.push(...kids);
+  }
+  insertBefore(kid) {
+    this.children.push(kid);
+  }
+  setAttribute(n, v) {
+    this.attrs[n] = String(v);
+    if (n === "class") this.className = v;
+  }
+  getAttribute(n) {
+    return this.attrs[n] ?? null;
+  }
+  hasAttribute(n) {
+    return n in this.attrs;
+  }
+  addEventListener(t, fn) {
+    (this.listeners[t] ??= []).push(fn);
+  }
+  click() {
+    (this.listeners.click ?? []).forEach((fn) => fn({ stopPropagation: () => undefined }));
+  }
+}
+globalThis.document = {
+  createElement: (t) => new Node(t),
+  createElementNS: (_n, t) => new Node(t),
+};
+
+function loadTs(file) {
+  const full = path.resolve(file);
+  if (cache.has(full)) return cache.get(full);
+  const js = ts.transpileModule(fs.readFileSync(full, "utf8"), {
+    compilerOptions: { module: ts.ModuleKind.CommonJS, target: ts.ScriptTarget.ES2020 },
+  }).outputText;
+  const box = { exports: {} };
+  cache.set(full, box.exports);
+  const req = (r) =>
+    r.startsWith("@util/")
+      ? loadTs(path.join(ROOT, "common_util", `${r.slice(6)}.ts`))
+      : loadTs(path.join(path.dirname(full), `${r}.ts`));
+  new Function("exports", "module", "require", js)(box.exports, box, req);
+  cache.set(full, box.exports);
+  return box.exports;
+}
+
+const pick = loadTs(path.join(ROOT, "B06_Section", "B06_Section_UI_Cross_Design_Pick.ts"));
+const x = (o) => 100 - o * 12; // +offset = 화면 왼쪽
+const y = (e) => 900 - (e - 100) * 12;
+const design = {
+  road_edges: {
+    left: { offset_m: 2, elevation_m: 100 },
+    right: { offset_m: -2, elevation_m: 100 },
+  },
+  ditch: null,
+  ditch_side: "left",
+  ditch_enabled: false,
+  section_mode: "both_fill",
+};
+const line = (pts) => {
+  const el = new Node("polyline");
+  el.setAttribute("class", "b06-chart__design-cross");
+  el.setAttribute("points", pts.map(([o, e]) => `${x(o)},${y(e)}`).join(" "));
+  el.setAttribute(pick.DESIGN_LINE_ATTR, "");
+  return el;
+};
+const layer = new Node("g");
+// 좌 성토 사면 · 노면 · 우 성토 사면
+layer.append(
+  line([
+    [6, 97],
+    [2, 100],
+  ]),
+  line([
+    [2, 100],
+    [-2, 100],
+  ]),
+  line([
+    [-2, 100],
+    [-6, 97],
+  ]),
+);
+const values = { left: 0, right: 0 };
+const handle = pick.attachDesignLinePick({
+  layer,
+  design,
+  x,
+  toDisplayY: y,
+  onPick: () => undefined,
+  shift: {
+    valueOf: (side) => values[side],
+    set: (side, v) => (values[side] = v),
+  },
+});
+const [left, right] = handle.label.children.filter((c) => c.tagName === "button");
+const pieceAt = (offset) =>
+  handle.pieces.findIndex(
+    (p) =>
+      Math.min(p.from.offset, p.to.offset) <= offset &&
+      offset <= Math.max(p.from.offset, p.to.offset),
+  );
+const log = [];
+handle.setActive(pieceAt(4)); // 좌 사면
+left.click(); // 화면 왼쪽 = 좌측 바깥 → +0.1
+left.click();
+log.push({ ...values });
+right.click(); // 안쪽 → 0.1
+right.click();
+right.click(); // 0 아래 금지
+log.push({ ...values });
+handle.setActive(pieceAt(-4)); // 우 사면
+left.click(); // 화면 왼쪽 = 우측 안쪽 → 0 에서 멈춤
+right.click(); // 우측 바깥 → +0.1
+log.push({ ...values });
+handle.setActive(pieceAt(-4));
+const text = handle.label.textContent;
+process.stdout.write(JSON.stringify({ log, text, buttons: [left.textContent, right.textContent] }));
diff --git a/resources/tester/test_139_6_line_shift.py b/resources/tester/test_139_6_line_shift.py
new file mode 100644
index 000000000..ae56ecd91
--- /dev/null
+++ b/resources/tester/test_139_6_line_shift.py
@@ -0,0 +1,48 @@
+"""139-6 고른 설계선 [◀ ▶] — 고른 조각 쪽 노견 확장 0.1 m 걸음 · 노폭 안쪽 금지(0 에서 멈춤).
+
+화면 TS(`_Cross_Design_Pick`)를 흉내 DOM 으로 돌린 값(`helper_139_6_line_shift.cjs`).
+"""
+
+import json
+import subprocess
+from pathlib import Path
+
+import pytest
+
+ROOT = Path(__file__).resolve().parents[2]
+HELPER = Path(__file__).parent / "helper_139_6_line_shift.cjs"
+
+pytestmark = pytest.mark.skipif(
+    not (ROOT / "config" / "node_modules").is_dir(), reason="프론트엔드 의존성 미설치"
+)
+
+
+@pytest.fixture(scope="module")
+def out() -> dict:
+    done = subprocess.run(  # noqa: S603 — 고정 실행 파일
+        ["node", str(HELPER)], cwd=str(ROOT), capture_output=True, text=True, encoding="utf-8"
+    )
+    assert done.returncode == 0, done.stderr
+    return json.loads(done.stdout)
+
+
+def test_화면_방향대로_그_쪽_노견만(out: dict) -> None:
+    first, back, right = out["log"]
+    assert first == {"left": 0.2, "right": 0}  # 좌 사면 고름 · ◀ 두 번 = 좌 바깥 0.2
+    assert back == {"left": 0, "right": 0}  # ▶ 세 번 = 0 에서 멈춤(노폭 안쪽 금지)
+    assert right == {"left": 0, "right": 0.1}  # 우 사면 · ◀ = 안쪽 0 · ▶ = 바깥 0.1
+
+
+def test_치수_줄에_노견_확장_표기(out: dict) -> None:
+    assert "노견 +0.1m" in out["text"]
+    assert out["buttons"] == ["◀", "▶"]
+
+
+def test_페이지가_같은_창구로_세션_재계산() -> None:
+    sync = (ROOT / "B06_Section" / "B06_Section_UI_Page_Design_Sync.ts").read_text(encoding="utf-8")
+    assert (
+        "writeShoulderExtend(projectId, currentRouteId, chainageM, shift.side, shift.valueM)"
+        in sync
+    )
+    persist = (ROOT / "B06_Section" / "B06_Section_UI_Page_Persist.ts").read_text(encoding="utf-8")
+    assert "patch.shoulder_extend_left_m = sides.left" in persist