1. A substrate surface inspecting apparatus comprising: a rotatable stage on which a substrate to be inspected is placed; an inspection optical system having one or more illumination light sources for emitting light to a substrate placed on the stage and one or more detectors for detecting reflection/scattering light from the substrate which is irradiated with the light from the illumination light sources; an A/D converter for amplifying and A/D converting signals output from the one or more detectors in the inspection optical system; and a defect detector for detecting defects in a surface of the substrate by processing signals output from the one or more detectors and converted by the A/D converter and classifying the defected defects, wherein the defect detector extracts micro defects in the surface of the substrate by processing the signals output from the one or more detectors, and detects linear defects existing discretely in a linear region from the extracted micro defects.