The present invention provides a scanning electron microscope (SEM) or optical inspection method and apparatus which correct differences in brightness between comparison images and thus which is capable of detecting a fine defect with a high degree of reliability without causing any false defect detection. According to the present invention, the brightness values of a pattern, which should be essentially the same, contained in two detected images to be compared are corrected in such a manner that, even if there may be a brightness difference in a portion free from defects, the brightness difference is reduced to such a degree so that it can be recognized as a normal portion. Also, a limit for the amount of correction is furnished in advance, and correction exceeding such limit value is not performed. Such correction prevents the difference in brightness that should be permitted as non-defective from being falsely recognized as a defect without overlooking great differences in brightness due to a defect.