「pic-background」クラスに「background-image」を制定し背景を設定。「background-size: cover;」で画像を全体を覆うように縮小させます。 <div class="container pic-background"></div> .pic-background { background-image: url(...); background-size: cover; background-position: center; } .container { position: relative; display: flex; justify-content: center; align-items: center; width: 100vw; height: 100vh; z-index: 0; }