diff --git a/Dockerfile b/Dockerfile
index 4e0d414..9b2ea4a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -9,7 +9,8 @@ RUN npm install
 
 # 소스 코드 복사 및 빌드
 COPY . .
-RUN npm run build
+RUN npm install -g @angular/cli
+RUN ng build
 
 # 2. Production Stage
 FROM node:24-alpine AS runner
diff --git a/src/app/app.html b/src/app/app.html
index 3cce3e0..9fffd72 100644
--- a/src/app/app.html
+++ b/src/app/app.html
@@ -3,20 +3,21 @@
 <div class="container">
   <h1>AEF Component Test</h1>
 
-  <section>
+  <section id="switch-test">
     <h2>Switch Component</h2>
     <switch [(isActive)]="isToggled" (toggle)="handleToggle($event)"></switch>
     <p>Switch is: {{ isToggled() ? 'ON' : 'OFF' }}</p>
   </section>
 
-  <section>
+  <section id="dropdown-test">
     <h2>Dropdown Component</h2>
     <div style="display: flex; flex-direction: column; gap: 40px; align-items: flex-start;">
       <div>
-        <h3>Object Options</h3>
+        <h3>Object Options (with defaultIndex="1")</h3>
         <dropdown
           [options]="dropdownOptions"
           [(value)]="selectedDropdownValue"
+          [defaultIndex]="1"
           (selectionChange)="handleDropdownChange($event)"
           icon="language">
         </dropdown>
diff --git a/src/app/app.scss b/src/app/app.scss
index 0cc6f1a..1d0e81e 100644
--- a/src/app/app.scss
+++ b/src/app/app.scss
@@ -27,3 +27,9 @@ p {
   margin-top: 15px;
   font-weight: 500;
 }
+
+section#dropdown-test {
+  dropdown {
+    width: 324px;
+  }
+}
diff --git a/src/app/components/dropdown/dropdown.ts b/src/app/components/dropdown/dropdown.ts
index 0d10d51..30c4a7f 100644
--- a/src/app/components/dropdown/dropdown.ts
+++ b/src/app/components/dropdown/dropdown.ts
@@ -1,4 +1,4 @@
-import { Component, input, model, output, signal, HostListener, ElementRef, computed
+import { Component, input, model, output, signal, HostListener, ElementRef, computed, OnInit
 } from '@angular/core'
 import { CommonModule } from '@angular/common'
 
@@ -30,11 +30,12 @@ export interface DropdownOption {
     '(keydown.arrowup)': 'onArrowUp($event)'
   }
 })
-export class Dropdown {
+export class Dropdown implements OnInit {
   options = input<Array<DropdownOption | string>>([]);
   placeholder = input<string>('Select an option');
   ariaLabel = input<string | undefined>(undefined);
   icon = input<string>();
+  defaultIndex = input<number>();
   value = model<any>(null);
   selectionChange = output<any>();
 
@@ -46,6 +47,16 @@ export class Dropdown {
 
   constructor(private el: ElementRef) {}
 
+  ngOnInit() {
+    const opts = this.normalizedOptions();
+    const dIndex = this.defaultIndex();
+    const currentValue = this.value();
+
+    if (currentValue === null && dIndex !== undefined && dIndex >= 0 && dIndex < opts.length) {
+      this.value.set(opts[dIndex].value);
+    }
+  }
+
   normalizedOptions = computed(() => {
     return this.options().map(opt => {
       if (typeof opt === 'string') {