In a defect inspecting apparatus, the strength of a fatal defect signal decreases due to miniaturization. Thus, in order to assure a high SN ratio, it is necessary to reduce noises caused by scattered light from a wafer. Roughness of a pattern edge and surface roughness which serve as a scattered-light source are spread over the entire wafer. The present invention has discovered the fact that reduction of an illuminated area is a technique effective for decreasing noises. That is to say, the present invention has discovered the fact that creation of an illuminated area having a spot shape and reduction of the dimension of a spot beam are effective. A plurality of temporally and spatially divided spot beams are radiated to the wafer serving as a sample.