In a spectroscopic ellipsometer, light emitted from a light source enters a measurement surface of a substrate through an optical system in a lighting part so as to incline to the measurement surface to be directed to a light receiving device, and ellipsometry is performed based on spectral intensity of reflected light reflected on the measurement surface, the spectral intensity being acquired by the light receiving device. In focusing of the spectroscopic ellipsometer, a focus position of the measurement surface is obtained based on a total light amount in a predetermined wavelength band of the reflected light, the total light amount being obtained by the light receiving device. In the spectroscopic ellipsometer, since the optical system for ellipsometry and the optical system for focusing are common, it is possible to eliminate influences of change of the optical systems by temperature change or the like and to achieve high accurate focusing.