An apparatus for detecting defects on a specimen including am illumination optical unit which obliquely projects a laser onto a region which is longer in one direction than in a direction transverse to said one direction on a surface of a specimen, a table unit which mounts said specimen and which is movable, a detection optical unit which detects with an image sensor an image of light formed by light reflected from said specimen in both directions of the one direction and the direction transverse and which reflected light in both directions is formed on said image sensor while said table is moving, a signal processor which processes a signal outputted from said image sensor of said detection optical unit to extract defects of said specimen. A display unit which displays information of defects extracted by said signal processor.