PURPOSE: To detect easily a scratch on a surface of specimen to be inspected, by installing a point light source on both sides each of a specimen surface in such a way that, a distance between these sources becomes equal to or less than the distance to the end of said surface to be inspected, and installing mirrors on the opposite sides.

CONSTITUTION: In each of transversal and longitudinal direcions of a surface 1 to be inspected having a mirror reflection characteristic, light sources 4, 5 are installed in such a way that a mounting distance L, L' is twice or less of a distance l, l' respectively. On the opposite sides of the sources 4, 5, mirrors 6, 7 are installed in such a way that, they are positioned through an angle of 90° with respect to the surface 1 to be inspected. Observation is performed of the surface 1 from an observation position 3. Scratches 2a, 2b are positioned at an angle of 90° to the source 41, the distance L of scratches 2c, 2d are equal to or less than twice of the distance l and so, an angle of reflected light and source 1 by the mirror 6 becomes 45° or more and both can be detected by comparing luminances. A scratch in the transversal direction can also be detected by mirror 7 and light source 5.