diff --git a/resources/tester/test_sheet_pages.py b/resources/tester/test_sheet_pages.py
index afeedecb..f2e74b7e 100644
--- a/resources/tester/test_sheet_pages.py
+++ b/resources/tester/test_sheet_pages.py
@@ -79,3 +79,36 @@ def test_page_rows_from_doc_and_master_single_page():
 def test_empty_doc_still_one_page_with_totals():
     plan = _plan({"양식": "시험", "종류": "표", "판": 1, "열": [], "줄": []})["project"]
     assert plan == [{"ids": [], "first": 1, "totals": True}]
+
+
+HEAD_SCRIPT = """
+const { setHeadLabel } = await import(process.argv[1]);
+const out = JSON.parse(process.argv[2]).map(([head, level, text, depth]) => {
+  setHeadLabel(head, level, text, depth);
+  return head;
+});
+console.log(JSON.stringify(out));
+"""
+
+
+def test_head_label_slash_splits_layers():
+    cases = [
+        [["새 열", None, None], 0, "관공/Φ800/관매설", 3],
+        [["새 열", None, None], 0, "관공/Φ800", 3],  # 적게 → 남은 층 합침
+        [["새 열", None, None], 0, "a/b/c/d", 3],  # 많으면 끝 층에 이어 붙임
+        [["종류", "공법", "규격"], 1, "이름", 3],  # / 없음 → 그 층만
+        [["새 열"], 0, "가/나", 3],  # 모자란 층은 채움
+    ]
+    result = subprocess.run(
+        ["node", "--experimental-strip-types", "--no-warnings", "--input-type=module", "-e",
+         HEAD_SCRIPT, OPS.as_uri(), json.dumps(cases, ensure_ascii=False)],
+        capture_output=True, text=True, encoding="utf-8", timeout=60,
+    )  # fmt: skip
+    assert result.returncode == 0, result.stderr
+    assert json.loads(result.stdout) == [
+        ["관공", "Φ800", "관매설"],
+        ["관공", "Φ800", None],
+        ["a", "b", "c/d"],
+        ["종류", "이름", "규격"],
+        ["가", "나", None],
+    ]
diff --git a/ui_template/sheet/ui_template_sheet.css b/ui_template/sheet/ui_template_sheet.css
index 35ee2794..e9a1f569 100644
--- a/ui_template/sheet/ui_template_sheet.css
+++ b/ui_template/sheet/ui_template_sheet.css
@@ -74,10 +74,10 @@
   text-align: center;
 }
 
-.ui-sheet__gutter {
+.ui-sheet__table .ui-sheet__gutter {
   position: sticky;
   left: 0;
-  z-index: 2;
+  z-index: 4;
   background: var(--color-surface) !important;
   color: var(--color-text-secondary);
   font-weight: 500;
@@ -176,6 +176,17 @@
   color: var(--color-accent);
 }
 
+.ui-sheet__headhint {
+  position: fixed;
+  z-index: 10;
+  padding: 2px 8px;
+  border: 1px solid var(--color-border);
+  border-radius: 4px;
+  background: var(--color-surface);
+  color: var(--color-text-secondary);
+  font-size: 0.76rem;
+}
+
 .ui-sheet__resize {
   position: absolute;
   top: 0;
diff --git a/ui_template/sheet/ui_template_sheet.ts b/ui_template/sheet/ui_template_sheet.ts
index 4b013afb..2249e240 100644
--- a/ui_template/sheet/ui_template_sheet.ts
+++ b/ui_template/sheet/ui_template_sheet.ts
@@ -20,7 +20,9 @@ import {
   type SheetMode,
   setCell,
   setColumnWidth,
+  setHeadLabel,
 } from "./ui_template_sheet_ops";
+import { headDepth } from "./ui_template_sheet_header";
 import { recalcSheet } from "./ui_template_sheet_recalc";
 import {
   KEY_UNIT,
@@ -123,6 +125,7 @@ export function createSheet(host: HTMLElement, input: SheetDoc, opts: SheetOptio
 
   // ── 그리기 · 고름 ─────────────────────────────────────────────────
   const render = (): void => {
+    root.querySelector(".ui-sheet__headhint")?.remove();
     state.result = recalcSheet(state.doc);
     const { scrollLeft, scrollTop } = scroll;
     scroll.replaceChildren(renderSheet(state));
@@ -200,13 +203,17 @@ export function createSheet(host: HTMLElement, input: SheetDoc, opts: SheetOptio
     const level = Number(th.dataset.level);
     if (start < 0 || Number.isNaN(level)) return;
     const span = state.doc.열.slice(start, start + (th as HTMLTableCellElement).colSpan);
+    const depth = headDepth(state.doc.열, state.doc.층);
+    const tip = el("div", { className: "ui-sheet__headhint", text: st("Head_Hint") });
+    const at = th.getBoundingClientRect();
+    tip.style.left = `${at.left}px`;
+    tip.style.top = `${at.bottom + 2}px`;
+    root.append(tip);
     startEdit(th, th.textContent ?? "", (value) => {
-      for (const col of span) {
-        while (col.머리.length <= level) col.머리.push(null);
-        col.머리[level] = value.trim();
-      }
+      for (const col of span) setHeadLabel(col.머리, level, value, depth);
       changed();
     });
+    th.querySelector("input")?.addEventListener("blur", () => tip.remove());
   };
 
   // ── 사건 ──────────────────────────────────────────────────────────
diff --git a/ui_template/sheet/ui_template_sheet_labels.ts b/ui_template/sheet/ui_template_sheet_labels.ts
index e86c37dc..f90b885d 100644
--- a/ui_template/sheet/ui_template_sheet_labels.ts
+++ b/ui_template/sheet/ui_template_sheet_labels.ts
@@ -76,7 +76,7 @@ export function formulaLabel(
 
 let ruler: CanvasRenderingContext2D | null = null;
 
-function textWidth(text: string, font: string): number {
+export function textWidth(text: string, font: string): number {
   ruler ??= document.createElement("canvas").getContext("2d");
   if (!ruler) return text.length * 13;
   ruler.font = font;
diff --git a/ui_template/sheet/ui_template_sheet_ops.ts b/ui_template/sheet/ui_template_sheet_ops.ts
index a4892174..e3d1be71 100644
--- a/ui_template/sheet/ui_template_sheet_ops.ts
+++ b/ui_template/sheet/ui_template_sheet_ops.ts
@@ -131,6 +131,22 @@ export function setCell(doc: SheetDoc, rowId: string, col: SheetColumn, text: st
   row.값[col.id] = typeof value === "number" && String(value) !== plain ? plain : value;
 }
 
+/** 머리 칸 고치기 — 글에 `/` 가 있으면 `level` 층부터 아래로 나눠 넣음(층보다 많으면 끝 층에 이어 붙임) ·
+ * 층보다 적게 쓰면 남은 층은 `null`(위 칸과 합침). `/` 가 없으면 그 층 글만 바꿈. */
+export function setHeadLabel(head: (string | null)[], level: number, text: string, depth: number) {
+  while (head.length <= level) head.push(null);
+  const parts = text.split("/").map((part) => part.trim());
+  if (parts.length < 2) {
+    head[level] = text.trim();
+    return;
+  }
+  const room = Math.max(1, depth - level);
+  const fit =
+    parts.length > room ? [...parts.slice(0, room - 1), parts.slice(room - 1).join("/")] : parts;
+  while (head.length < depth) head.push(null);
+  for (let k = level; k < depth; k += 1) head[k] = fit[k - level] ?? null;
+}
+
 export function setColumnWidth(doc: SheetDoc, id: string, width: number): void {
   doc.보기 ??= {};
   (doc.보기.열너비 ??= {})[id] = Math.round(width);
diff --git a/ui_template/sheet/ui_template_sheet_render.ts b/ui_template/sheet/ui_template_sheet_render.ts
index 2d9ab72c..7bef596f 100644
--- a/ui_template/sheet/ui_template_sheet_render.ts
+++ b/ui_template/sheet/ui_template_sheet_render.ts
@@ -9,7 +9,7 @@
 
 import { el } from "@ui/ui_template_elements";
 import { headDepth, layoutHead } from "./ui_template_sheet_header";
-import { columnNames, formulaLabel, headMinWidths } from "./ui_template_sheet_labels";
+import { columnNames, formulaLabel, headMinWidths, textWidth } from "./ui_template_sheet_labels";
 import {
   cellEditable,
   isBoundColumn,
@@ -24,7 +24,8 @@ import type { SheetColumn, SheetDoc, SheetResult, SheetRow } from "./ui_template
 
 export const KEY_UNIT = "s:unit";
 const MASTER_ROWS = ["s:formula", "s:desc", "s:price"] as const;
-const GUTTER = 64;
+const GUTTER_MIN = 64;
+const GUTTER_MAX = 140;
 const DEFAULT_WIDTH = { 수: 72, 글: 96 };
 
 export interface RenderState {
@@ -85,7 +86,23 @@ export function renderSheet(state: RenderState): HTMLElement {
   const depth = headDepth(cols, doc.층);
   const head = layoutHead(cols, depth);
   const names = columnNames(cols);
-  const mins = headMinWidths(cols, depth, headFont());
+  const font = headFont();
+  const mins = headMinWidths(cols, depth, font);
+  // 줄 머리 칸 폭 — 층 이름 · 단위 · 식 · 들어갈 것 · 일위대가 · 합계 이름이 안 잘리게
+  const GUTTER = Math.min(
+    GUTTER_MAX,
+    Math.max(
+      GUTTER_MIN,
+      ...[
+        ...(doc.층 ?? []),
+        st("Row_Unit"),
+        st("Row_Formula"),
+        st("Row_Desc"),
+        st("Row_Unit_Price"),
+        ...(doc.합계줄 ?? []).map((t) => t.이름),
+      ].map((label) => Math.ceil(textWidth(label, font)) + 16),
+    ),
+  );
   const errors = new Map(state.result.오류.map((e) => [`d:${e.줄}|${e.열}`, e.까닭]));
   for (const e of state.result.오류) errors.set(`t:${e.줄}|${e.열}`, e.까닭);
   const frozen = Math.min(doc.보기?.틀고정?.열 ?? 0, cols.length);
diff --git a/ui_template/sheet/ui_template_sheet_text.ts b/ui_template/sheet/ui_template_sheet_text.ts
index 37ac1a63..6dd8d091 100644
--- a/ui_template/sheet/ui_template_sheet_text.ts
+++ b/ui_template/sheet/ui_template_sheet_text.ts
@@ -21,6 +21,10 @@ const TEXT = {
   Kind_Hand: ["손 입력", "Manual"],
   Kind_Spread: ["값마다 열", "Per value"],
   Page: ["쪽", "page"],
+  Head_Hint: [
+    "/ 로 이으면 층으로 나뉨 (예 관공/Φ800/관매설) · 적게 쓰면 남은 층은 위 칸과 합침",
+    "Use / to split into layers (e.g. A/B/C) · fewer parts merge the rest with the cell above",
+  ],
   Error: ["#오류", "#ERR"],
   Hint: [
     "칸을 누르고 바로 치거나 Enter · F2 로 고침 · = 로 시작하면 그 칸만 식 · 화살표 · Tab 으로 옮김 · Delete 로 비움",