diff --git a/TypeScript/app/gilded-rose.ts b/TypeScript/app/gilded-rose.ts
index 15d316bf..31bf931f 100644
--- a/TypeScript/app/gilded-rose.ts
+++ b/TypeScript/app/gilded-rose.ts
@@ -1,72 +1,19 @@
-import { ITEMS } from "./constants";
-
-export class Item {
-  name: string;
-  sellIn: number;
-  quality: number;
-
-  constructor(name, sellIn, quality) {
-    this.name = name;
-    this.sellIn = sellIn;
-    this.quality = quality;
-  }
-}
+import { AgedBrie, Passes, Surfras } from "./itemClasses";
+type ItemClasses = AgedBrie[] | Surfras[] | Passes[];
 
 export class GildedRose {
-  items: Array<Item>;
-
-  constructor(items = [] as Array<Item>) {
+  items: ItemClasses;
+  constructor(items = [] as ItemClasses) {
     this.items = items;
   }
 
-  handlePassesQuality(item) {
-    if (item.name !== ITEMS.PASSES) return;
-    if (6 <= item.sellIn && item.sellIn < 11) {
-      item.quality += 1;
-    }
-
-    if (item.sellIn < 6) {
-      item.quality += 2;
-    }
-  }
-
-  handleIfSellInIs0(item) {
-    if (item.sellIn >= 0) return;
-
-    switch (item.name) {
-      case ITEMS.BRIE:
-        if (item.quality >= 50) return;
-        item.quality = item.quality + 1;
-        break;
-      case ITEMS.SURFRAS:
-        item.quality = 0;
-        break;
-      default:
-        if (!item.quality) return;
-        item.quality -= 1;
-        break;
-    }
-  }
-
   updateQuality() {
-    for (const item of this.items) {
-      if (!item.quality) break;
-      if (item.name != ITEMS.SURFRAS) {
-        item.sellIn -= 1;
-      }
-      this.handleIfSellInIs0(item);
+    const updatedItems = this.items.map((item) => {
+      item.handleSellIn();
+      item.handleQuality();
 
-      if (item.name != ITEMS.BRIE && item.name != ITEMS.PASSES) {
-        if (item.name === ITEMS.SURFRAS) break;
-        item.quality -= 1;
-      }
-
-      if (item.quality >= 50) break;
-      item.quality += 1;
-
-      this.handlePassesQuality(item);
-    }
-
-    return this.items;
+      return item;
+    });
+    return updatedItems as ItemClasses;
   }
 }
diff --git a/TypeScript/app/itemClasses.ts b/TypeScript/app/itemClasses.ts
new file mode 100644
index 00000000..8a1b6aac
--- /dev/null
+++ b/TypeScript/app/itemClasses.ts
@@ -0,0 +1,66 @@
+export class Item {
+  name: string;
+  sellIn: number;
+  quality: number;
+
+  constructor(name, sellIn, quality) {
+    this.name = name;
+    this.sellIn = sellIn;
+    this.quality = quality;
+  }
+}
+
+export class AgedBrie extends Item {
+  constructor(sellIn, quality) {
+    super("Aged Brie", sellIn, quality);
+  }
+  handleQuality() {
+    if (this.quality >= 50 || this.quality === 0) return;
+    if (this.sellIn === 0) {
+      this.quality = this.quality / 2;
+      return;
+    }
+    this.quality++;
+  }
+
+  handleSellIn() {
+    this.sellIn--;
+  }
+}
+
+export class Passes extends Item {
+  constructor(sellIn, quality) {
+    super("Backstage passes to a TAFKAL80ETC concert", sellIn, quality);
+  }
+
+  handleQuality() {
+    if (this.quality >= 50 || this.quality === 0) return;
+
+    if (this.sellIn === 0) {
+      this.quality = 0;
+      return;
+    }
+
+    if (6 <= this.sellIn && this.sellIn < 11) {
+      this.quality += 2;
+    }
+
+    if (this.sellIn < 6) {
+      this.quality += 3;
+    }
+  }
+
+  handleSellIn() {
+    this.sellIn--;
+  }
+}
+
+export class Surfras extends Item {
+  constructor(sellIn, quality) {
+    super("Sulfuras, Hand of Ragnaros", sellIn, quality);
+  }
+
+  handleQuality() {}
+
+  handleSellIn() {}
+}
diff --git a/TypeScript/test/golden-master-text-test.ts b/TypeScript/test/golden-master-text-test.ts
index 6fa5537a..3ee77ab2 100644
--- a/TypeScript/test/golden-master-text-test.ts
+++ b/TypeScript/test/golden-master-text-test.ts
@@ -1,4 +1,5 @@
-import { Item, GildedRose } from "../app/gilded-rose";
+import { Item } from "@/itemClasses";
+import { GildedRose } from "../app/gilded-rose";
 
 const items = [
   new Item("+5 Dexterity Vest", 10, 20), //
diff --git a/TypeScript/test/jest/gilded-rose.spec.ts b/TypeScript/test/jest/gilded-rose.spec.ts
index e89a60f6..664a5072 100644
--- a/TypeScript/test/jest/gilded-rose.spec.ts
+++ b/TypeScript/test/jest/gilded-rose.spec.ts
@@ -1,10 +1,11 @@
-import { Item, GildedRose } from "@/gilded-rose";
+import { GildedRose } from "@/gilded-rose";
+import { AgedBrie, Passes, Surfras } from "@/itemClasses";
 
 describe("Aged Brie 테스트", () => {
-  let gildedRose = new GildedRose([new Item("Aged Brie", 1, 0)]);
+  let gildedRose = new GildedRose([new AgedBrie(1, 0)]);
 
   beforeEach(() => {
-    gildedRose = new GildedRose([new Item("Aged Brie", 2, 3)]);
+    gildedRose = new GildedRose([new AgedBrie(2, 3)]);
   });
 
   it("Aged Brie의 quality는 1 증가, sellIn은 1 감소", () => {
@@ -15,21 +16,35 @@ describe("Aged Brie 테스트", () => {
   });
 
   it("quality는 50을 초과할 수 없음", () => {
-    const gildedRose = new GildedRose([new Item("Aged Brie", 2, 50)]);
+    const gildedRose = new GildedRose([new AgedBrie(2, 50)]);
     const items = gildedRose.updateQuality();
 
     expect(items[0].sellIn).toBe(1);
     expect(items[0].quality).toBe(50);
   });
+
+  it("quality는 음수가 될 수 없음", () => {
+    const gildedRose = new GildedRose([new AgedBrie(2, 0)]);
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].sellIn).toBe(1);
+    expect(items[0].quality).toBe(0);
+  });
+
+  it("sellIn값이 0이 되면 Quality는 2배로 감소", () => {
+    const gildedRose = new GildedRose([new AgedBrie(1, 4)]);
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].sellIn).toBe(0);
+    expect(items[0].quality).toBe(2);
+  });
 });
 
 describe("Surfras 테스트", () => {
-  let gildedRose = new GildedRose([
-    new Item("Sulfuras, Hand of Ragnaros", 1, 0),
-  ]);
+  let gildedRose = new GildedRose([new Surfras(1, 0)]);
 
   beforeEach(() => {
-    gildedRose = new GildedRose([new Item("Sulfuras, Hand of Ragnaros", 2, 3)]);
+    gildedRose = new GildedRose([new Surfras(2, 3)]);
   });
 
   it("Surfras의 quality는 변하지 않음, sellIn 변하지 않음", () => {
@@ -41,14 +56,10 @@ describe("Surfras 테스트", () => {
 });
 
 describe("Backstage passes 테스트", () => {
-  let gildedRose = new GildedRose([
-    new Item("Backstage passes to a TAFKAL80ETC concert", 1, 0),
-  ]);
+  let gildedRose = new GildedRose([new Passes(1, 0)]);
 
   beforeEach(() => {
-    gildedRose = new GildedRose([
-      new Item("Backstage passes to a TAFKAL80ETC concert", 2, 3),
-    ]);
+    gildedRose = new GildedRose([new Passes(2, 3)]);
   });
 
   it("Backstage passes의 sellIn값 1감소, quality 1증가", () => {
@@ -59,9 +70,7 @@ describe("Backstage passes 테스트", () => {
   });
 
   it("Backstage passes의 sellIn값 10일부터, quality 2증가", () => {
-    const gildedRose = new GildedRose([
-      new Item("Backstage passes to a TAFKAL80ETC concert", 10, 3),
-    ]);
+    const gildedRose = new GildedRose([new Passes(10, 3)]);
     const items = gildedRose.updateQuality();
 
     expect(items[0].sellIn).toBe(9);
@@ -69,12 +78,34 @@ describe("Backstage passes 테스트", () => {
   });
 
   it("Backstage passes의 sellIn값 5일부터, quality 3증가", () => {
-    const gildedRose = new GildedRose([
-      new Item("Backstage passes to a TAFKAL80ETC concert", 5, 3),
-    ]);
+    const gildedRose = new GildedRose([new Passes(5, 3)]);
     const items = gildedRose.updateQuality();
 
     expect(items[0].sellIn).toBe(4);
     expect(items[0].quality).toBe(6);
   });
+
+  it("Backstage passes의 sellIn값 0일 때, quality 0으로 변경", () => {
+    const gildedRose = new GildedRose([new Passes(1, 3)]);
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].sellIn).toBe(0);
+    expect(items[0].quality).toBe(0);
+  });
+
+  it("quality는 50을 초과할 수 없음", () => {
+    const gildedRose = new GildedRose([new AgedBrie(2, 50)]);
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].sellIn).toBe(1);
+    expect(items[0].quality).toBe(50);
+  });
+
+  it("quality는 음수가 될 수 없음", () => {
+    const gildedRose = new GildedRose([new Passes(1, 0)]);
+    const items = gildedRose.updateQuality();
+
+    expect(items[0].sellIn).toBe(0);
+    expect(items[0].quality).toBe(0);
+  });
 });