A two-dimensional sensor is installed inclining at a predetermined angle to a moving direction of a stage on which an object to be inspected is mounted and, in synchronism with the movement of the stage, a picked up image is rearranged so that there can be obtained an image in high-density sampling with a picture-element size or less of the two-dimensional sensor with respect to a wafer. Thus, interpolation calculation during position alignment becomes unnecessary, and size calculation and classification of a defect can be performed with high accuracy.