To measure and inspect the deformation of an entire optical disk at a low cost by obliquely projecting a plurality of light beams emitted from pin holes arrayed in a straight manner on pin hole plate and receiving reflected light beams thereof with a two-dimensional CCD camera.

A laser sport emitted from a semiconductor laser 5 is converted into a parallel light by a collimator lens 13, this light is spread in a fan shape by a cylinder lens 4 and a light flux thereof is converted into a parallel light by an fθ lens 3. The lens passed through the lens 3 is passed through a plurality of pin holes on a pin hole plate 2, being arrayed on a straight line in the radial portion of an optical disk 1, and made to be plural light beams, and obliquely made incident on the optical disk 1. In a two-dimensional CCD camera 6 composed of light emitting and receiving systems, these systems are passed through the optical disk 1 and symmetrically arranged via a flat surface 7 perpendicular to the flat surface of the optical disk and the deformation of the optical disk is measured based on a deviation from the correct position of the image forming position of the light receiving part of the camera 6.