1. An inspection apparatus comprising: an illumination section for illuminating an inspection target in accordance with a photometric stereo method; an imaging section for receiving reflective light from the illuminated inspection target to generate a luminance image in accordance with the photometric stereo method; a computing section for calculating a normal vector of a surface of the inspection target from a plurality of luminance images acquired by the imaging section, generating 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, and performing synthesis processing of synthesizing at least two images out of the inclination image and the at least one reduced image, to generate an inspection image showing a surface shape of the inspection target; a determination section for determining defectiveness/non-defectiveness of the inspection target by using the inspection image; and a setting section for setting a characteristic size which is a parameter for giving weight to a component of the reduced image at the time of performing the synthesis processing, wherein the computing section generates a different inspection image in accordance with the characteristic size set by the setting section.