- 利用 grid
<div class="wrap">
<div class="box"></div>
<div class="box"></div>
<div class="box"></div>
</div>
<style>
.wrap {
display: grid;
grid-template-columns: 1fr 1fr;
}
.box {
height: 50px;
background-color: #332;
margin: 10px;
}
.box:first-child {
grid-column-start: span 2;
}
</style>