A defect inspecting apparatus can detect finer defects with high resolution optical images of those defects. The apparatus includes a sample mounting device for mounting a sample; lighting and detecting apparatus for illuminating a patterned sample mounted on a mount and detecting the optical image of the reflected light obtained therefrom. A display displays the optical image detected by this lighting and detecting apparatus. An optical parameter setting device sets and displays optical parameters for the lighting and detecting apparatus on the display. An optical parameter adjusting apparatus adjusts optical parameters set for the lighting and detecting apparatus according to the optical parameters set by the optical parameter setting apparatus. A storage device stores comparative image data. A defect detecting device detects defects from patterns formed on the sample by comparing the optical image detected by the optical image detecting apparatus with the comparative image data stored in the storage.