To provide a new method for estimating an etching depth, in particular, a method for estimating an etching depth having higher accuracy than conventional methods have, and a method for evaluating element concentration distribution in a depth direction by using this method.

In this method for estimating an etching depth, an etching rate is found as a ratio between etching depths and sputtering periods or dose amounts from two or more sets of sputtering periods or dose amounts of sputter etching caused by ion beam application and etching depths for determining an etching depth at an arbitrary sputtering period or a dose amount from the etching rate. In this estimation method, an etching depth is dealt with as a constant at a certain sputtering period or a dose amount to find etching rates on subsequent sputtering periods or dose amounts.