diff --git a/tksupport/api/models/vacationBalanceModel.js b/tksupport/api/models/vacationBalanceModel.js
index 444aa82..f8063de 100644
--- a/tksupport/api/models/vacationBalanceModel.js
+++ b/tksupport/api/models/vacationBalanceModel.js
@@ -61,24 +61,76 @@ const vacationBalanceModel = {
     return result;
   },
 
+  // 우선순위: 이월 → 기본연차 → 추가부여 → 장기근속 → 회사부여
   async deductDays(userId, vacationTypeId, year, daysToDeduct, conn) {
     const db = conn || getPool();
-    const [result] = await db.query(`
-      UPDATE sp_vacation_balances
-      SET used_days = used_days + ?, updated_at = NOW()
-      WHERE user_id = ? AND vacation_type_id = ? AND year = ?
-    `, [daysToDeduct, userId, vacationTypeId, year]);
-    return result;
+    const needRelease = !conn;
+    const c = needRelease ? await db.getConnection() : db;
+    try {
+      if (needRelease) await c.beginTransaction();
+
+      const [balances] = await c.query(`
+        SELECT id, total_days, used_days, (total_days - used_days) AS remaining_days, balance_type
+        FROM sp_vacation_balances
+        WHERE user_id = ? AND year = ? AND (total_days - used_days) > 0
+        ORDER BY FIELD(balance_type, 'CARRY_OVER', 'AUTO', 'MANUAL', 'LONG_SERVICE', 'COMPANY_GRANT')
+        FOR UPDATE
+      `, [userId, year]);
+
+      let remaining = daysToDeduct;
+      for (const b of balances) {
+        if (remaining <= 0) break;
+        const toDeduct = Math.min(remaining, parseFloat(b.remaining_days));
+        if (toDeduct > 0) {
+          await c.query('UPDATE sp_vacation_balances SET used_days = used_days + ?, updated_at = NOW() WHERE id = ?', [toDeduct, b.id]);
+          remaining -= toDeduct;
+        }
+      }
+
+      if (needRelease) await c.commit();
+      return { affectedRows: balances.length };
+    } catch (err) {
+      if (needRelease) await c.rollback();
+      throw err;
+    } finally {
+      if (needRelease) c.release();
+    }
   },
 
+  // 복원: 역순 (회사부여 → 장기근속 → 추가부여 → 기본연차 → 이월)
   async restoreDays(userId, vacationTypeId, year, daysToRestore, conn) {
     const db = conn || getPool();
-    const [result] = await db.query(`
-      UPDATE sp_vacation_balances
-      SET used_days = GREATEST(0, used_days - ?), updated_at = NOW()
-      WHERE user_id = ? AND vacation_type_id = ? AND year = ?
-    `, [daysToRestore, userId, vacationTypeId, year]);
-    return result;
+    const needRelease = !conn;
+    const c = needRelease ? await db.getConnection() : db;
+    try {
+      if (needRelease) await c.beginTransaction();
+
+      const [balances] = await c.query(`
+        SELECT id, used_days, balance_type
+        FROM sp_vacation_balances
+        WHERE user_id = ? AND year = ? AND used_days > 0
+        ORDER BY FIELD(balance_type, 'COMPANY_GRANT', 'LONG_SERVICE', 'MANUAL', 'AUTO', 'CARRY_OVER')
+        FOR UPDATE
+      `, [userId, year]);
+
+      let remaining = daysToRestore;
+      for (const b of balances) {
+        if (remaining <= 0) break;
+        const toRestore = Math.min(remaining, parseFloat(b.used_days));
+        if (toRestore > 0) {
+          await c.query('UPDATE sp_vacation_balances SET used_days = used_days - ?, updated_at = NOW() WHERE id = ?', [toRestore, b.id]);
+          remaining -= toRestore;
+        }
+      }
+
+      if (needRelease) await c.commit();
+      return { affectedRows: balances.length };
+    } catch (err) {
+      if (needRelease) await c.rollback();
+      throw err;
+    } finally {
+      if (needRelease) c.release();
+    }
   },
 
   calculateAnnualLeaveDays(hireDate, targetYear) {