diff --git a/src/components/floor-plan/modal/basic/step/ModuleTabContents.jsx b/src/components/floor-plan/modal/basic/step/ModuleTabContents.jsx
index 9fd7da9a..70f1f1ab 100644
--- a/src/components/floor-plan/modal/basic/step/ModuleTabContents.jsx
+++ b/src/components/floor-plan/modal/basic/step/ModuleTabContents.jsx
@@ -1,6 +1,5 @@
 import { useState, useEffect } from 'react'
 import { useMessage } from '@/hooks/useMessage'
-import { isObjectNotEmpty } from '@/util/common-utils'
 import QSelectBox from '@/components/common/select/QSelectBox'
 import { useModuleTabContents } from '@/hooks/module/useModuleTabContents'
 import { useRecoilValue } from 'recoil'
@@ -170,41 +169,32 @@ export default function ModuleTabContents({ tabIndex, addRoof, setAddedRoofs, ro
           </div>
           <div className="module-flex-item non-flex">
             <div className="flex-item-btn-wrap">
-              <button
-                className={`btn-frame roof ${isObjectNotEmpty(constructionList[0]) && constructionList[0].constPossYn === 'Y' ? 'white' : ''}`}
-                ref={(el) => (constructionRef.current[0] = el)}
-                onClick={() => (isObjectNotEmpty(constructionList[0]) && constructionList[0].constPossYn === 'Y' ? handleConstruction(0) : null)}
-              >
-                標準施工(Ⅰ)
-              </button>
-              <button
-                className={`btn-frame roof ${isObjectNotEmpty(constructionList[3]) && constructionList[3].constPossYn === 'Y' ? 'white' : ''}`}
-                ref={(el) => (constructionRef.current[3] = el)}
-                onClick={() => (isObjectNotEmpty(constructionList[3]) && constructionList[3].constPossYn === 'Y' ? handleConstruction(3) : null)}
-              >
-                多設施工
-              </button>
-              <button
-                className={`btn-frame roof ${isObjectNotEmpty(constructionList[1]) && constructionList[1].constPossYn === 'Y' ? 'white' : ''}`}
-                ref={(el) => (constructionRef.current[1] = el)}
-                onClick={() => (isObjectNotEmpty(constructionList[1]) && constructionList[1].constPossYn === 'Y' ? handleConstruction(1) : null)}
-              >
-                標準施工
-              </button>
-              <button
-                className={`btn-frame roof ${isObjectNotEmpty(constructionList[4]) && constructionList[4].constPossYn === 'Y' ? 'white' : ''}`}
-                ref={(el) => (constructionRef.current[4] = el)}
-                onClick={() => (isObjectNotEmpty(constructionList[4]) && constructionList[4].constPossYn === 'Y' ? handleConstruction(4) : null)}
-              >
-                多設施工（II）
-              </button>
-              <button
-                className={`btn-frame roof ${isObjectNotEmpty(constructionList[2]) && constructionList[2].constPossYn === 'Y' ? 'white' : ''}`}
-                ref={(el) => (constructionRef.current[2] = el)}
-                onClick={() => (isObjectNotEmpty(constructionList[2]) && constructionList[2].constPossYn === 'Y' ? handleConstruction(2) : null)}
-              >
-                強化施工
-              </button>
+              {/* 2026-06-05 공법 버튼을 배열 인덱스 대신 constTp로 매핑 — API 응답 항목 추가/순서변경(예: 標準施工(Ⅱ) WORK_LV_ID_-2) 시 인덱스 밀림 방지. 운영(구 API)엔 -2가 없어 optional 은 데이터 있을 때만 렌더 */}
+              {[
+                { constTp: 'WORK_LV_ID_-1', label: '標準施工(Ⅰ)' },
+                { constTp: 'WORK_LV_ID_-2', label: '標準施工(Ⅱ)', optional: true },
+                { constTp: 'WORK_LV_ID_1', label: '標準施工' },
+                { constTp: 'WORK_LV_ID_3', label: '強化施工' },
+                { constTp: 'WORK_LV_ID_4', label: '多設施工' },
+                { constTp: 'WORK_LV_ID_5', label: '多設施工（II）' },
+              ].map(({ constTp, label, optional }) => {
+                const index = constructionList.findIndex((c) => c.constTp === constTp)
+                const item = index > -1 ? constructionList[index] : null
+                if (optional && !item) return null
+                const enabled = item && item.constPossYn === 'Y'
+                return (
+                  <button
+                    key={constTp}
+                    className={`btn-frame roof ${enabled ? 'white' : ''}`}
+                    ref={(el) => {
+                      if (index > -1) constructionRef.current[index] = el
+                    }}
+                    onClick={() => (enabled ? handleConstruction(index) : null)}
+                  >
+                    {label}
+                  </button>
+                )
+              })}
             </div>
             <div className="grid-check-form-block">
               <div className="d-check-box pop">
diff --git a/src/components/floor-plan/modal/basic/step/Trestle.jsx b/src/components/floor-plan/modal/basic/step/Trestle.jsx
index dd2e64ca..98a4c4ee 100644
--- a/src/components/floor-plan/modal/basic/step/Trestle.jsx
+++ b/src/components/floor-plan/modal/basic/step/Trestle.jsx
@@ -217,7 +217,7 @@ const Trestle = forwardRef((props, ref) => {
   }, [constructionList, autoSelectStep])
 
   const getConstructionState = (index) => {
-    if (constructionList && constructionList.length > 0) {
+    if (index > -1 && constructionList && constructionList.length > 0 && constructionList[index]) {
       if (constructionList[index].constPossYn === 'Y') {
         if (trestleState && trestleState.constTp === constructionList[index].constTp) {
           return 'blue'
@@ -865,21 +865,23 @@ const Trestle = forwardRef((props, ref) => {
             </div>
             <div className="module-flex-item non-flex">
               <div className="flex-item-btn-wrap">
-                <button className={`btn-frame roof ${getConstructionState(0)}`} onClick={() => handleConstruction(0)}>
-                  {getMessage('modal.module.basic.setting.module.standard.construction')}(I)
-                </button>
-                <button className={`btn-frame roof ${getConstructionState(3)}`} onClick={() => handleConstruction(3)}>
-                  {getMessage('modal.module.basic.setting.module.multiple.construction')}
-                </button>
-                <button className={`btn-frame roof ${getConstructionState(1)}`} onClick={() => handleConstruction(1)}>
-                  {getMessage('modal.module.basic.setting.module.standard.construction')}
-                </button>
-                <button className={`btn-frame roof ${getConstructionState(4)}`} onClick={() => handleConstruction(4)}>
-                  {getMessage('modal.module.basic.setting.module.multiple.construction')}(II)
-                </button>
-                <button className={`btn-frame roof ${getConstructionState(2)}`} onClick={() => handleConstruction(2)}>
-                  {getMessage('modal.module.basic.setting.module.enforce.construction')}
-                </button>
+                {/* 2026-06-05 공법 버튼을 배열 인덱스 대신 constTp로 매핑 — API 응답 항목 추가/순서변경(예: 標準施工(II) WORK_LV_ID_-2) 시 인덱스 밀림 방지. 운영(구 API)엔 -2가 없어 optional 은 데이터 있을 때만 렌더 */}
+                {[
+                  { constTp: 'WORK_LV_ID_-1', label: `${getMessage('modal.module.basic.setting.module.standard.construction')}(I)` },
+                  { constTp: 'WORK_LV_ID_-2', label: `${getMessage('modal.module.basic.setting.module.standard.construction')}(II)`, optional: true },
+                  { constTp: 'WORK_LV_ID_1', label: getMessage('modal.module.basic.setting.module.standard.construction') },
+                  { constTp: 'WORK_LV_ID_3', label: getMessage('modal.module.basic.setting.module.enforce.construction') },
+                  { constTp: 'WORK_LV_ID_4', label: getMessage('modal.module.basic.setting.module.multiple.construction') },
+                  { constTp: 'WORK_LV_ID_5', label: `${getMessage('modal.module.basic.setting.module.multiple.construction')}(II)` },
+                ].map(({ constTp, label, optional }) => {
+                  const index = constructionList.findIndex((c) => c.constTp === constTp)
+                  if (optional && index === -1) return null
+                  return (
+                    <button key={constTp} className={`btn-frame roof ${getConstructionState(index)}`} onClick={() => handleConstruction(index)}>
+                      {label}
+                    </button>
+                  )
+                })}
               </div>
               <div className="grid-check-form-flex">
                 <div className="d-check-box pop">
diff --git a/src/hooks/module/useModuleTabContents.js b/src/hooks/module/useModuleTabContents.js
index 5f82f939..7fe24f64 100644
--- a/src/hooks/module/useModuleTabContents.js
+++ b/src/hooks/module/useModuleTabContents.js
@@ -175,9 +175,10 @@ export function useModuleTabContents({ tabIndex, addRoof, setAddedRoofs, roofTab
       isObjectNotEmpty(moduleConstructionSelectionData?.construction) &&
       moduleConstructionSelectionData?.construction.hasOwnProperty('constPossYn') ///키가 있으면
     ) {
-      const selectedIndex = moduleConstructionSelectionData.construction.selectedIndex
-      const construction = constructionList[selectedIndex]
-      if (construction.constPossYn === 'Y') {
+      // 2026-06-05 저장값 복원도 constTp 기준 — 항목 추가/순서변경으로 selectedIndex 가 어긋나는 문제 방지
+      const selectedIndex = constructionList.findIndex((c) => c.constTp === moduleConstructionSelectionData.construction.constTp)
+      const construction = selectedIndex > -1 ? constructionList[selectedIndex] : null
+      if (construction && construction.constPossYn === 'Y') {
         handleConstruction(selectedIndex)
       }
     }
@@ -268,7 +269,7 @@ export function useModuleTabContents({ tabIndex, addRoof, setAddedRoofs, roofTab
   const handleConstruction = (index) => {
     if (index > -1) {
       const isPossibleIndex = constructionRef.current
-        .map((el, i) => (el.classList.contains('white') || el.classList.contains('blue') ? i : -1))
+        .map((el, i) => (el && (el.classList.contains('white') || el.classList.contains('blue')) ? i : -1))
         .filter((index) => index !== -1)
 
       isPossibleIndex.forEach((index) => {
@@ -341,7 +342,7 @@ export function useModuleTabContents({ tabIndex, addRoof, setAddedRoofs, roofTab
       setSelectedConstruction(selectedConstruction)
     } else {
       constructionRef.current.forEach((ref) => {
-        ref.classList.remove('blue')
+        if (ref) ref.classList.remove('blue')
       })
     }
   }