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 a plurality of reduced images of the inclination image with respectively different reduction ratios, and performing synthesis processing of synthesizing at least two reduced images, 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 wherein the computing section gives weight to a component of the reduced images at the time of performing the synthesis processing and generates a different inspection image in accordance with a characteristic size which is a parameter showing a size of a surface shape of the inspection target.