1. A semiconductor device defect inspection method comprising the steps of: specifying inspection points by a defect type on design data; selecting a pre-specified number of inspection points from the specified inspection points, by the defect type; imaging the pre-specified number of inspection points selected by the defect type, and detecting defects at the inspection points; calculating a defect ratio of the detected defects with respect to the number of inspection points imaged by the defect type and also a confidence interval of the defect ratio; comparing the confidence interval of the defect ratio calculated by the defect type with a preset reference value; and obtaining a defect type having a defect occurrence ratio exceeding the reference value.