An apparatus for inspecting defects including a table which mounts a specimen to be inspected and which is movable in a plane, an ultraviolet light source for emitting ultraviolet light, an illuminating unit for illuminating the specimen mounted on the table with light emitted from the ultraviolet light source, a detecting unit for forming an image of the specimen illuminated by the illuminating unit and for detecting the image with an image sensor, and an image processing unit for processing the image detected by the image sensor and for outputting information about defects detected on the specimen. The illuminating unit and detecting unit are disposed in a clean environment which is supplied therein with clean gas and which is separated from outside by a wall.