Abstract: A defect inspection apparatus inspects a defect by a compare check method even if there is only one object substrate to be inspected. Further, if there are a plurality of object substrates to be inspected, the defect inspection apparatus corrects a reference pattern image in accordance with defect inspection using the compare check method. In application to a printed to wire board on which identical unit patterns are printed, unit patterns which are included in one row are defined as a mater area and the other unit patterns on the same printed wire board are defined as object areas. The master area is compared with each one of the object areas to thereby perform defect inspection. When there are a plurality of object substrates to be inspected, a pattern image is corrected utilizing results of comparison. By using a corrected pattern image as a master substrate image, defect inspection is performed on the other object substrates.