A pattern inspection apparatus includes: an optical image acquiring unit configured to acquire optical image data of a target object on which each of a plurality of identical patterns is respectively formed at a respective corresponding position of a plurality of forming positions with distortion; a cut-out unit configured to cut out a plurality of partial optical image data from the optical image data; a correction unit configured to correct positions of the plurality of partial optical image data by using distortion information from which each amount of distortion of the plurality of identical patterns respectively formed at the respective corresponding position of the plurality of forming positions on the target object can be acquired; and a comparison unit configured to compare a plurality of corrected partial optical image data against each other on a pixel to pixel basis.