diff --git a/backend/internal/domain/auth_models.go b/backend/internal/domain/auth_models.go
index 8167ce35..5358c738 100644
--- a/backend/internal/domain/auth_models.go
+++ b/backend/internal/domain/auth_models.go
@@ -87,10 +87,11 @@ type UserProfileResponse struct {
 }
 
 type UpdateUserRequest struct {
-	Name             string `json:"name"`
-	Phone            string `json:"phone"`
-	Department       string `json:"department"`
-	VerificationCode string `json:"verificationCode,omitempty"` // For phone change
+	Name             string         `json:"name"`
+	Phone            string         `json:"phone"`
+	Department       string         `json:"department"`
+	VerificationCode string         `json:"verificationCode,omitempty"` // For phone change
+	Metadata         map[string]any `json:"metadata,omitempty"`
 }
 
 // PasswordResetInitiateRequest is the request body for initiating a password reset.
diff --git a/backend/internal/handler/auth_handler.go b/backend/internal/handler/auth_handler.go
index dcae0d06..03faed40 100644
--- a/backend/internal/handler/auth_handler.go
+++ b/backend/internal/handler/auth_handler.go
@@ -5266,6 +5266,39 @@ func (h *AuthHandler) UpdateMe(c *fiber.Ctx) error {
 		traits["department"] = req.Department
 	}
 
+	// Merge custom metadata into traits
+	if len(req.Metadata) > 0 {
+		for k, v := range req.Metadata {
+			// Do not overwrite core fields
+			if _, isCore := map[string]bool{"email": true, "phone_number": true, "name": true, "department": true, "grade": true, "companyCode": true, "affiliationType": true, "id": true, "role": true, "tenant_id": true}[k]; !isCore {
+				traits[k] = v
+			}
+		}
+	}
+
+	// [LoginID Sync based on Tenant Settings]
+	schemaCompCode := extractTraitString(traits, "companyCode")
+	if schemaCompCode != "" && h.TenantService != nil {
+		if tenant, err := h.TenantService.GetTenantBySlug(c.Context(), schemaCompCode); err == nil && tenant != nil {
+			if loginIDField, ok := tenant.Config["loginIdField"].(string); ok && loginIDField != "" {
+				// Search in Metadata (could be flat or namespaced)
+				if val, exists := req.Metadata[loginIDField]; exists {
+					if loginIDStr, ok := val.(string); ok && loginIDStr != "" {
+						traits["id"] = loginIDStr
+					}
+				} else if namespaced, exists := req.Metadata[tenant.ID]; exists {
+					if subMeta, ok := namespaced.(map[string]any); ok {
+						if val, exists := subMeta[loginIDField]; exists {
+							if loginIDStr, ok := val.(string); ok && loginIDStr != "" {
+								traits["id"] = loginIDStr
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+
 	if err := h.updateKratosIdentity(identityID, traits); err != nil {
 		slog.Error("Failed to update profile in Kratos", "error", err)
 		return errorJSON(c, fiber.StatusInternalServerError, "프로필 업데이트에 실패했습니다.")