Result

jQuery

var maxHeight = 0;
//もしdivがmaxHeightの値より大きい場合はdivの高さを全部合わせる
$("div").each(function(){
   if ($(this).height() > maxHeight) { maxHeight = $(this).height(); }
});
//divの高さを取得する
$("div").height(maxHeight);

css

div{
    height:auto;
    width: 70px ;
    background:#eee;
    margin:3px;
    float:left;
}

html

<div>1<br />2<br />3<br />4<br />5</div>

<div>div</div>

<div>div</div>

<div>div</div>

<div></div>

<div>1<br />2<br />3<br />4<br />5<br />6<br />7<br />8<br />9</div>

<div></div>

via

Equalize Heights of Divs | CSS-Tricks

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