diff --git a/app/Models/Tenants/WorkSetting.php b/app/Models/Tenants/WorkSetting.php
index 5776968..38ba09b 100644
--- a/app/Models/Tenants/WorkSetting.php
+++ b/app/Models/Tenants/WorkSetting.php
@@ -42,7 +42,7 @@ class WorkSetting extends Model
     ];
 
     protected $casts = [
-        'work_days' => 'array',
+        // work_days는 Attribute accessor에서 처리
         'standard_hours' => 'integer',
         'overtime_hours' => 'integer',
         'overtime_limit' => 'integer',
@@ -79,6 +79,65 @@ class WorkSetting extends Model
 
     public const DEFAULT_WORK_DAYS = ['mon', 'tue', 'wed', 'thu', 'fri'];
 
+    /**
+     * 숫자 → 요일 문자열 매핑
+     */
+    public const DAY_INDEX_MAP = [
+        1 => 'mon',
+        2 => 'tue',
+        3 => 'wed',
+        4 => 'thu',
+        5 => 'fri',
+        6 => 'sat',
+        7 => 'sun',
+        0 => 'sun', // 일요일이 0인 경우도 처리
+    ];
+
+    // =========================================================================
+    // Accessors & Mutators
+    // =========================================================================
+
+    /**
+     * work_days 조회 시 숫자를 문자열로 변환
+     */
+    protected function workDays(): \Illuminate\Database\Eloquent\Casts\Attribute
+    {
+        return \Illuminate\Database\Eloquent\Casts\Attribute::make(
+            get: function ($value) {
+                $days = is_string($value) ? json_decode($value, true) : $value;
+
+                if (! is_array($days)) {
+                    return self::DEFAULT_WORK_DAYS;
+                }
+
+                // 숫자가 포함된 경우 문자열로 변환
+                return array_values(array_unique(array_map(function ($day) {
+                    if (is_int($day) || is_numeric($day)) {
+                        return self::DAY_INDEX_MAP[(int) $day] ?? 'mon';
+                    }
+
+                    return $day;
+                }, $days)));
+            },
+            set: function ($value) {
+                if (! is_array($value)) {
+                    return json_encode(self::DEFAULT_WORK_DAYS);
+                }
+
+                // 항상 문자열 배열로 저장
+                $days = array_values(array_unique(array_map(function ($day) {
+                    if (is_int($day) || is_numeric($day)) {
+                        return self::DAY_INDEX_MAP[(int) $day] ?? 'mon';
+                    }
+
+                    return $day;
+                }, $value)));
+
+                return json_encode($days);
+            }
+        );
+    }
+
     // =========================================================================
     // 헬퍼 메서드
     // =========================================================================