<style>
	.att01 div	{
		border:dotted 1px red;
		margin: 10px; padding: 10px;
	}
</style>
<script>
	$(function(){
		var ele01 = $('.att01 div:first-child').attr('class');
		$('.att01 .eleclass02').text(ele01);
	});
</script>
<div class="att01">
	<div class="eleclass01">要素1</div>
	<div class="eleclass02">要素2</div>
</div>