PURPOSE: To decide defectiveness and nondefectiveness of masks with high accuracy by making the form of the model defects observed with an inspecting device for mask defects to coincide with the defects formed on wafers.

CONSTITUTION: The 1st model defects 3 and the 2nd model defects 4 are formed in the prescribed area of the transferred pattern area 2 of a mask 1. This mask 1 is set in an automatic inspecting device for mask defects where light 10 is transmitted therethrough and the images 12a, 12b of the 1st and the 2nd model defects 3, 4 are displayed on respective displays 13a, 13b via detecting heads 11a, 11b. Prescribed patterns are transferred with the mask 1 on the wafer and the defects in the transferred patterns are detected with a microscope. The detected defects are made to coincide with the primary defects 15a displayed on the part 15. By the coincidence operation, the defects on the wafer are decided. Thus the defectiveness and non-defectiveness of the mask is decided with high accuracy by making the primary defect data and the defect on the wafer to coincide.