diff --git a/src/hooks/roofcover/useWallLineOffsetSetting.js b/src/hooks/roofcover/useWallLineOffsetSetting.js
index e9e22ea8..bfe2c4b0 100644
--- a/src/hooks/roofcover/useWallLineOffsetSetting.js
+++ b/src/hooks/roofcover/useWallLineOffsetSetting.js
@@ -516,6 +516,14 @@ export function useWallLineOffsetSetting(id) {
       }
     }
 
+    // 좌표가 변경된 라인의 planeSize/actualSize 재계산 — 길이 라벨은 attributes.planeSize 저장값을 표시하므로
+    // 재계산 없이 fire('modified') 만 하면 이전 길이가 그대로 남는다.
+    ;[currentLine, prevLine, nextLine].forEach((line) => {
+      if (!line?.attributes) return
+      const newSize = calcLinePlaneSize({ x1: line.x1, y1: line.y1, x2: line.x2, y2: line.y2 })
+      line.attributes = { ...line.attributes, planeSize: newSize, actualSize: newSize }
+    })
+
     const newOuterLines = canvas.getObjects().filter((obj) => obj.name === 'outerLine')
     newOuterLines.sort((a, b) => a.idx - b.idx)
     newOuterLines.forEach((line, idx) => {