DEFECT INSPECTION METHOD

An image picked up by a detection system capable of actualizing a three-dimensional inclination is usually poor in the signal-to-noise ratio, and it is difficult to stably detect minute defects. Images that actualize a three-dimensional inclination are picked up from opposed directions. The images are subject to subtraction and addition. The images improved in signal-to-noise ratio as compared with original images are calculated. The images calculated and improved in signal-to-noise ratio respectively of a defect portion and a reference portion are compared with each other. Regions differing in comparison results are detected as defects. As a result, minute defects can be inspected stably.