To precisely perform inspection of flaws, contaminants, foreign substances, air bubbles, stress distortion, etc. by comparatively simple configuration without using image analysis of lens images.

Polarizing plates 13a and 13b polarize optical beams oscillated from a pair of semiconductor lasers 10a and 10b in mutually orthogonal directions. A half-wavelength plate 12 rotates a polarizing face of one optical beam up to 180 degrees. A beam splitter 14 superposes the two optical beams. The superposed optical beam is incident on a lens to be inspected 19 by being reflected on entire reflective mirrors 15 and 16. The optical beam passing the lens to be inspected 19 is separated on a half-mirror 20, condensed with condenser lenses 21a and 21b, and is incident on photodiodes 23a and 23b by being polarized with the polarizing plates 21a and 21b in the mutually orthogonal directions.