diff --git a/TypeScript/app/gilded-rose.ts b/TypeScript/app/gilded-rose.ts
index 5404c076..31bf931f 100644
--- a/TypeScript/app/gilded-rose.ts
+++ b/TypeScript/app/gilded-rose.ts
@@ -9,9 +9,9 @@ export class GildedRose {
 
   updateQuality() {
     const updatedItems = this.items.map((item) => {
+      item.handleSellIn();
       item.handleQuality();
 
-      item.handleSellIn();
       return item;
     });
     return updatedItems as ItemClasses;
diff --git a/TypeScript/app/itemClasses.ts b/TypeScript/app/itemClasses.ts
index b89da25e..8a1b6aac 100644
--- a/TypeScript/app/itemClasses.ts
+++ b/TypeScript/app/itemClasses.ts
@@ -15,7 +15,11 @@ export class AgedBrie extends Item {
     super("Aged Brie", sellIn, quality);
   }
   handleQuality() {
-    if (this.quality >= 50) return;
+    if (this.quality >= 50 || this.quality === 0) return;
+    if (this.sellIn === 0) {
+      this.quality = this.quality / 2;
+      return;
+    }
     this.quality++;
   }
 
@@ -30,14 +34,20 @@ export class Passes extends Item {
   }
 
   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 += 1;
+      this.quality += 2;
     }
 
     if (this.sellIn < 6) {
-      this.quality += 2;
+      this.quality += 3;
     }
-    this.quality++;
   }
 
   handleSellIn() {
@@ -49,11 +59,8 @@ export class Surfras extends Item {
   constructor(sellIn, quality) {
     super("Sulfuras, Hand of Ragnaros", sellIn, quality);
   }
-  handleQuality() {
-    //
-  }
 
-  handleSellIn() {
-    //
-  }
+  handleQuality() {}
+
+  handleSellIn() {}
 }
diff --git a/TypeScript/test/jest/gilded-rose.spec.ts b/TypeScript/test/jest/gilded-rose.spec.ts
index 3f0f0c64..664a5072 100644
--- a/TypeScript/test/jest/gilded-rose.spec.ts
+++ b/TypeScript/test/jest/gilded-rose.spec.ts
@@ -22,6 +22,22 @@ describe("Aged Brie 테스트", () => {
     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", () => {
@@ -68,4 +84,28 @@ describe("Backstage passes 테스트", () => {
     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);
+  });
 });