PURPOSE: To attain to simplify flaw inspection work, by providing a first optical system constituted so that the signal surface thereof comes to a focus matching surface and a second optical system constituted so that the surface comes to a focus matching surface and providing a light detector detecting the reflected lights from said respective focus matching surfaces.

CONSTITUTION: Beam is formed into an image on the signal surface 7 of an optical information recording medium disk D to obtain a minute spot 9 and the reflected beam from the signal surface 7 due to said minute sport 9 is incident on a first beam detector PD1 by an objective lens OL and the beam paths of first and second half mirrors MH1, MH2. The electric signal corresponding to the information of the signal surface 7 of the disk D is outputted from a light detector PD1. Laser beam is incident on an auxiliary lens AL and the beam passed through said lens AL is converged by the objective lens OL and formed into an image on the surface of the cover glass of the disk D to obtain a minute spot 9 and the reflected beam due to said spot 9 is incident to a second beam detector PD2 by the objective lens OL and the beam paths of he first second half mirrors MH1, MH2. The electric signal corresponding to the information on the surface of the cover glass layer 6 of the disk D is obtained from the second beam detector PD2.