PURPOSE: To make it possible to progress.a mask to the ensuing processing regardless of the varying speeds of development of design patterns by storing one of optical pattern information in one auxiliary storage device, reducing out this information and comparing with design pattern information.

CONSTITUTION: The optical image of the mask 2 is formed by an optical system consisting of a photoirradiating section 1 and a lens system 3, is processed by a photoelectric conversion section 4 and is outputted as optical patterns 5a and 5b which are electrical information. The optical pattern information 5a obtd. in order to compare and inspect the patterns in the mask 2 with each other is previously stored in an auxiliary storage device 10, such as hard disk, and the comparison with the design pattern information 9 obtd. by developing design data 8 is executed by reading out the stored information and, therefore, the need for keeping the mask 2 which is the examinee in the inspection apparatus is eliminated. Then, the mask is progressed to the ensuing stage right after reading of the optical information for the purpose of comparison and inspection within the mask, by which the delay occurring in the mask inspection is eliminated.