To discriminate whether on not an IC is defective caused by a defect part when the IC is manufactured by using a photomask having the defect part.

A verifying process for verifying generated pattern data for verification is performed by using (a) an image extracting process for extracting defect image data of image data to be processed by performing exclusive OR graphic operation for the image data to be processed which are obtained by a photomask defect inspecting device, (b) a verifying data generating process for generating pattern data for verification by generating polygon data that a design tool can inputs from the outline of the defect of the extracted defect image data and putting together the generated polygon data and design data, and (c) a verifying device. According to the result of the verifying process, it is discriminated whether or not the place corresponding to the processing object image data of the photomask is a fatal factor causing a circuit defect when the IC is manufacture.