To provide a secondary ion mass spectrometry capable of specifying the position of a compound film/substrate interface by measuring the concentration and the distribution of a trace element highly sensitively and highly quantitatively, and specifying the position of a compound film/substrate interface, concerning material having information of an elemental composition of the polar surface of a sample and an interface such as the compound film/substrate or the like.

A primary ion beam is irradiated onto the surface of the sample having the interface between the substrate and the compound film containing a main constitutive element of the substrate, and simultaneously gas which is a nonmetal element existing in the compound film and is formed by concentrating an isotope having a small abundance ratio of the nonmetal element is introduced continuously, absorbed and concentrated on the sample surface, and simultaneously the secondary ion is detected by a mass spectrometer. By optimizing the quantity of the introduced gas and an irradiation condition of the primary ion beam, a matrix effect between the compound and the substrate is removed, and simultaneously the position of the compound film/substrate interface can be specified.