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 configured to emit light to a substrate placed on the stage, and one or more detectors configured to detect reflection/scattering light reflected or scattered from the substrate irradiated with light from the illumination light sources; an A/D converter configured to amplify and to A/D convert signals output from the one or more detectors in the inspection optical system; and a defect detector configured to detect defects existing in a surface of the substrate, by processing signals output from the one or more detectors and converted by the A/D converter, and to classify the defected defects, wherein the defect detector is configured to extract defects existing in the surface of the substrate, including micro defects, by processing the signals output from the one or more detectors, to detect continuous linear defects, and to detect, from the extracted micro defects, discrete linear defects that exist in a linear region of the surface of the substrate.