To provide a method for analyzing impurity profiles to easily perform secondary ion mass spectrometry with high resolution in the depth direction.

This method is a method for analyzing impurity profiles using secondary ion mass spectrometry, and comprises a process to prepare an SOI base plate comprising a top silicon layer 1, a BOX oxide film 7 and a support base plate 8, a process to perform semiconductor production process on the layer 1, a process to paste a glass substrate 11 on the surface of the layer 1, a process to remove the plate 8 from the SOI base plate by mechanical polishing, a process to remove the layer 7 from the SOI base plate by etching with hydrofluoric acid for exposing the top silicon layer, and a process to analyze the top silicon layer from the rear face direction using secondary ion mass spectrometry.