PURPOSE: To measure the fabrication error of aspheric surface with high accuracy by applying the constitution that a transmission type inspection object positioning computer hologram to generate transmission diffraction light for setting the suitable position of inspection surface is formed on a flat plate.

CONSTITUTION: A transmission type measurement computer hologram 3 is formed on a flat plate (glass substrate) 2 in such state as capable of generating a wave front to measure inspection surface 1a relative to the prescribed incident light wave front. Also, a transmission type inspection object positioning computer hologram 4 is formed to generate transmissive diffraction light for setting the suitable position of the surface 1a relative to the hologram 3. In addition, a substrate positioning computer hologram 11 is formed to generate reflected diffraction light forming a phase conjugate wave front relative to the incident light wave front. Then, spherical or flat reflection surface is formed on a jig 20 holding an inspection object 1, and the position of the plate 2 is aligned. Thereafter, the plate 2 is moved by the preset distance and the hologram 3 is aligned, thereby measuring the surface 1a.