According to a defect inspecting method implemented in a semiconductor circuit inspection machine, a difference in a gray-scale level of a pattern edge image is corrected. A procedure of determining a magnitude of correction is modified in efforts to improve the sensitivity in detecting a defective pattern edge image. A defect inspecting system comprises: an image alignment unit that detects a sub-pixel deviation of two images, which are objects of inspection, from each other; and a magnitude-of-correction determination unit that determines a magnitude of correction, by which the difference in a gray-scale level of a pattern edge image between the two images that is detected by the difference detector is corrected, according to the detected sub-pixel deviation.