A photometric processing part calculates a normal vector of a surface of a workpiece from a plurality of luminance images acquired by a camera in accordance with the photometric stereo method, and performs synthesis processing of synthesizing at least two images out of an inclination image made up of pixel values based on the normal vector calculated from the plurality of luminance images and at least one reduced image of the inclination image, to generate an inspection image showing a surface shape of the inspection target. In particular, a characteristic size setting part sets a characteristic size which is a parameter for giving weight to a component of a reduced image at the time of performing the synthesis processing. The photometric processing part can generate a different inspection image in accordance with the set characteristic size.