The island structure of indium has been investigated by employing the depth profile measurement of XPS. Indium films of 30∼180 nm (in mass thickness) were deposited on silicon substrate by vacuum evaporation at 80°C. The island structure was confirmed by AFM as the substrate surface was filled with islands. In an XPS apparatus, films were sputter-etched with Ar ion to obtain the depth profile. On plotting the XPS signals of In and Si against the sputter time normalized by the deposited amount, the depth profiles of films of various thicknesses were found to have a curve in common. We can explain this universal relation by a model in which the islands of the same form completely cover the substrate surface, and shrink as they are sputtered keeping their similarity. The agreement of the experimental result with our model also suggests that the In islands do not change their form during the growth.