To enhance the common defect decision accuracy in wafer defect inspection of a semiconductor device.

A defect sorting/processing section 13 affixes a defect classification to a detected defect depending on the type thereof. A grouping means 142 affixes an identical group umber to defects which have been retrieved as being at the same position by a coordinate comparing means 141. A defect number totalizing means 143 totalizes the defects belonging to each group for each classification, calculates the ratio of the umber of shots where a defect belonging to that defect classification exists to the total number of inspection shots and determines the largest value as the ratio of the number of shots having defect for that group. It the ratio thus determined exceeds a threshold value, a common defect decision means 144 decides that a defect belonging to that group is a common defect.