A method for evaluating a thin-film-formed wafer, being configured to calculate a film thickness distribution of a thin film of the thin-film-formed wafer having the thin film on a surface of a substrate, wherein light having a single wavelength λ is applied to a partial region of a surface of the thin-film-formed wafer, reflected light from the region is detected, reflected light intensity for each pixel obtained by dividing the region into many pieces is measured, a reflected light intensity distribution in the region is obtained, and the film thickness distribution of the thin film in the region is calculated from the reflected light intensity distribution. The method enables a film thickness distribution of the micro thin film (an SOI layer) that affects a device to be measured on the entire wafer surface at a low cost with a sufficient spatial resolution in a simplified manner.