An inspection method of an SOI wafer in which profiles P1 and P2 are calculated in the SOI wafer to be inspected and in an SOI wafer having a film thickness of the SOI layer thicker or thinner than that of the SOI wafer to be inspected, respectively; a profile P3 of a difference between P1 and P2, or a profile P4 of a change ratio of P1 and P2 is calculated; light having the wavelength band selected on the basis of a maximum peak wavelength within the calculated profiles P3 or P4 is irradiated to the surface of the SOI wafer to be inspected, to detect the reflected-light from the SOI wafer; and a place of a peak generated by an increase in reflection intensity of the detected reflected-light is found, as the defect caused by the change in the film thickness of the SOI layer.