diff --git a/lib/src/core/engine/market_service.dart b/lib/src/core/engine/market_service.dart
new file mode 100644
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--- /dev/null
+++ b/lib/src/core/engine/market_service.dart
@@ -0,0 +1,166 @@
+import 'package:asciineverdie/data/game_text_l10n.dart' as l10n;
+import 'package:asciineverdie/src/core/engine/potion_service.dart';
+import 'package:asciineverdie/src/core/engine/shop_service.dart';
+import 'package:asciineverdie/src/core/model/equipment_slot.dart';
+import 'package:asciineverdie/src/core/model/game_state.dart';
+import 'package:asciineverdie/src/core/model/item_stats.dart';
+import 'package:asciineverdie/src/core/util/deterministic_random.dart';
+import 'package:asciineverdie/src/core/util/pq_logic.dart' as pq_logic;
+
+/// 판매 처리 결과
+class SellResult {
+  const SellResult({
+    required this.state,
+    required this.continuesSelling,
+  });
+
+  final GameState state;
+  final bool continuesSelling;
+}
+
+/// 시장/판매/구매 서비스
+///
+/// ProgressService에서 분리된 시장 로직 담당:
+/// - 장비 구매
+/// - 아이템 판매
+/// - 골드 관리
+class MarketService {
+  const MarketService({required this.rng});
+
+  final DeterministicRandom rng;
+
+  /// 인벤토리에서 Gold 수량 반환
+  int getGold(GameState state) {
+    return state.inventory.gold;
+  }
+
+  /// 장비 구매 완료 처리 (개선된 로직)
+  ///
+  /// 1순위: 빈 슬롯에 Common 장비 최대한 채우기
+  /// 2순위: 골드 남으면 물약 구매
+  GameState completeBuying(GameState state) {
+    var nextState = state;
+    final level = state.traits.level;
+    final shopService = ShopService(rng: rng);
+
+    // 1. 빈 슬롯 목록 수집
+    final emptySlots = <int>[];
+    for (var i = 0; i < Equipment.slotCount; i++) {
+      if (nextState.equipment.getItemByIndex(i).isEmpty) {
+        emptySlots.add(i);
+      }
+    }
+
+    // 2. 골드가 허용하는 한 빈 슬롯에 Common 장비 구매
+    for (final slotIndex in emptySlots) {
+      final slot = EquipmentSlot.values[slotIndex];
+      final item = shopService.generateShopItem(
+        playerLevel: level,
+        slot: slot,
+        targetRarity: ItemRarity.common,
+      );
+      final price = shopService.calculateBuyPrice(item);
+
+      if (nextState.inventory.gold >= price) {
+        nextState = nextState.copyWith(
+          inventory: nextState.inventory.copyWith(
+            gold: nextState.inventory.gold - price,
+          ),
+          equipment: nextState.equipment
+              .setItemByIndex(slotIndex, item)
+              .copyWith(bestIndex: slotIndex),
+        );
+      } else {
+        break; // 골드 부족 시 중단
+      }
+    }
+
+    // 3. 물약 자동 구매 (남은 골드의 20% 사용)
+    final potionService = const PotionService();
+    final purchaseResult = potionService.autoPurchasePotions(
+      playerLevel: level,
+      inventory: nextState.potionInventory,
+      gold: nextState.inventory.gold,
+      spendRatio: 0.20,
+    );
+
+    if (purchaseResult.success && purchaseResult.newInventory != null) {
+      nextState = nextState.copyWith(
+        inventory: nextState.inventory.copyWith(gold: purchaseResult.newGold),
+        potionInventory: purchaseResult.newInventory,
+      );
+    }
+
+    return nextState;
+  }
+
+  /// 판매 처리
+  ///
+  /// [state] 현재 게임 상태
+  /// Returns: 업데이트된 상태와 판매 계속 여부
+  SellResult processSell(GameState state) {
+    final taskType = state.progress.currentTask.type;
+    var items = [...state.inventory.items];
+    var goldAmount = state.inventory.gold;
+
+    // sell 태스크 완료 시 아이템 판매 (원본 Main.pas:636-643)
+    if (taskType == TaskType.sell) {
+      // 첫 번째 아이템 찾기 (items에는 Gold가 없음)
+      if (items.isNotEmpty) {
+        final item = items.first;
+        final level = state.traits.level;
+
+        // 가격 계산: 수량 * 레벨
+        var price = item.count * level;
+
+        // " of " 포함 시 보너스 (원본 639-640)
+        if (item.name.contains(' of ')) {
+          price =
+              price *
+              (1 + pq_logic.randomLow(rng, 10)) *
+              (1 + pq_logic.randomLow(rng, level));
+        }
+
+        // 아이템 삭제
+        items.removeAt(0);
+
+        // Gold 추가 (inventory.gold 필드 사용)
+        goldAmount += price;
+      }
+    }
+
+    // 판매할 아이템이 남아있는지 확인
+    final hasItemsToSell = items.isNotEmpty;
+
+    if (hasItemsToSell) {
+      // 다음 아이템 판매 태스크 시작
+      final nextItem = items.first;
+      final translatedName = l10n.translateItemNameL10n(nextItem.name);
+      final itemDesc = l10n.indefiniteL10n(translatedName, nextItem.count);
+      final taskResult = pq_logic.startTask(
+        state.progress,
+        l10n.taskSelling(itemDesc),
+        1 * 1000,
+      );
+      final progress = taskResult.progress.copyWith(
+        currentTask: TaskInfo(caption: taskResult.caption, type: TaskType.sell),
+        currentCombat: null, // 비전투 태스크이므로 전투 상태 초기화
+      );
+      return SellResult(
+        state: state.copyWith(
+          inventory: state.inventory.copyWith(gold: goldAmount, items: items),
+          progress: progress,
+        ),
+        continuesSelling: true,
+      );
+    }
+
+    // 판매 완료 - 인벤토리 업데이트만 하고 다음 태스크로
+    return SellResult(
+      state: state.copyWith(
+        inventory: state.inventory.copyWith(gold: goldAmount, items: items),
+      ),
+      continuesSelling: false,
+    );
+  }
+}