PURPOSE: To accurately measure the diameter or degree of concentricity of a hole made in a measured body, by shooting modulatory light into a holographic lens having a plurality of foci, then irradiating the light upon the measured body and analyzing a signal of the light reflected from the body.

CONSTITUTION: Laser light L emitted from a laser light oscillator is caused to perform prescribed modulation by a polarizer 2. The oscillatory light is entered into a holographic lens having a plurality of foci which are located in prescribed positions due to holography. The light is irradiated upon a mesured body 6 positioned on the foci. The oscillatory light reflected from the body 6 is changed into an electric signal by a sensor 10. The electric signal is processed to detect the dimensional accuracy of the body 6. A plurality of parts of the body 6 can be automatically and simultaneously measured with high accuracy.