diff --git a/backend-node/src/routes/dataRoutes.ts b/backend-node/src/routes/dataRoutes.ts
index 0abc6793..02dfc1e8 100644
--- a/backend-node/src/routes/dataRoutes.ts
+++ b/backend-node/src/routes/dataRoutes.ts
@@ -742,6 +742,7 @@ router.post(
         inserted: result.data?.inserted || 0,
         updated: result.data?.updated || 0,
         deleted: result.data?.deleted || 0,
+        savedIds: result.data?.savedIds || [],
       });
     } catch (error) {
       console.error("그룹화된 데이터 UPSERT 오류:", error);
diff --git a/backend-node/src/services/dataService.ts b/backend-node/src/services/dataService.ts
index 8c837697..2150a4af 100644
--- a/backend-node/src/services/dataService.ts
+++ b/backend-node/src/services/dataService.ts
@@ -1519,11 +1519,12 @@ class DataService {
         }
       }
 
-      console.log(`✅ UPSERT 완료:`, { inserted, updated, deleted });
+      const savedIds = Array.from(processedIds);
+      console.log(`✅ UPSERT 완료:`, { inserted, updated, deleted, savedIds });
 
       return {
         success: true,
-        data: { inserted, updated, deleted },
+        data: { inserted, updated, deleted, savedIds },
       };
     } catch (error) {
       console.error(`UPSERT 오류 (${tableName}):`, error);
diff --git a/frontend/lib/api/data.ts b/frontend/lib/api/data.ts
index 270c59f9..14aad709 100644
--- a/frontend/lib/api/data.ts
+++ b/frontend/lib/api/data.ts
@@ -238,7 +238,7 @@ export const dataApi = {
     parentKeys: Record<string, any>,
     records: Array<Record<string, any>>,
     options?: { deleteOrphans?: boolean }
-  ): Promise<{ success: boolean; inserted?: number; updated?: number; deleted?: number; message?: string; error?: string }> => {
+  ): Promise<{ success: boolean; inserted?: number; updated?: number; deleted?: number; savedIds?: string[]; message?: string; error?: string }> => {
     try {
       console.log("📡 [dataApi.upsertGroupedRecords] 요청 데이터:", {
         tableName,
diff --git a/frontend/lib/registry/components/selected-items-detail-input/SelectedItemsDetailInputComponent.tsx b/frontend/lib/registry/components/selected-items-detail-input/SelectedItemsDetailInputComponent.tsx
index e73a78c6..ffe2875d 100644
--- a/frontend/lib/registry/components/selected-items-detail-input/SelectedItemsDetailInputComponent.tsx
+++ b/frontend/lib/registry/components/selected-items-detail-input/SelectedItemsDetailInputComponent.tsx
@@ -689,6 +689,8 @@ export const SelectedItemsDetailInputComponent: React.FC<SelectedItemsDetailInpu
               // 레코드에 id(기존 DB PK)가 있으면 EDIT 모드 → 고아 삭제
               // id 없으면 CREATE 모드 → 기존 레코드 건드리지 않음
               const mappingHasDbIds = mappingRecords.some((r) => !!r.id);
+              // 저장된 매핑 ID를 추적 (디테일 테이블에 mapping_id 주입용)
+              let savedMappingIds: string[] = [];
               try {
                 const mappingResult = await dataApi.upsertGroupedRecords(
                   mainTable,
@@ -696,6 +698,11 @@ export const SelectedItemsDetailInputComponent: React.FC<SelectedItemsDetailInpu
                   mappingRecords,
                   { deleteOrphans: mappingHasDbIds },
                 );
+                // 백엔드에서 반환된 저장된 레코드 ID 목록
+                if (mappingResult.success && mappingResult.savedIds) {
+                  savedMappingIds = mappingResult.savedIds;
+                  console.log(`✅ ${mainTable} 저장 완료, savedIds:`, savedMappingIds);
+                }
               } catch (err) {
                 console.error(`❌ ${mainTable} 저장 실패:`, err);
               }
@@ -755,6 +762,18 @@ export const SelectedItemsDetailInputComponent: React.FC<SelectedItemsDetailInpu
                   priceRecords.push(emptyRecord);
                 }
 
+                // Step1에서 저장된 매핑 ID를 디테일 레코드에 주입
+                // (customer_item_prices.mapping_id ← customer_item_mapping.id)
+                if (savedMappingIds.length > 0) {
+                  const mappingId = savedMappingIds[0]; // 일반적으로 1:N (매핑 1개 : 단가 N개)
+                  priceRecords.forEach((record) => {
+                    if (!record.mapping_id) {
+                      record.mapping_id = mappingId;
+                    }
+                  });
+                  console.log(`🔗 디테일 레코드에 mapping_id 주입: ${mappingId}`);
+                }
+
                 const priceHasDbIds = priceRecords.some((r) => !!r.id);
                 try {
                   const detailResult = await dataApi.upsertGroupedRecords(