In the conventional methods for enhancing defect detection sensitivity by improving the resolving power, if a microscopic pattern, which is a high spatial-frequency structure as is the case with a microscopic defect, has become the brightest portion, the gray-scale contrast of the microscopic defect will be enhanced. At the same time, however, the gray-scale contrast of the microscopic pattern will also be enhanced simultaneously. Consequently, there has existed a problem that it is impossible to enhance the microscopic-defect detection sensitivity further than that. In the present invention, an aperture stop which is divided into a plurality of small apertures is located on an illumination pupil plane. Then, light-shield/light-transmission for each small aperture is controlled independently of each other. This control allows an inspection-target object to be illuminated at only an incident angle at which the gray-scale contrast of the microscopic defect will be emphasized more sharply.