A surface inspection device and method wherein an illumination system is arranged so that light from a laser diode is transformed into parallel light which is then directed through a half waveplate to a surface of a reticle to be inspected. A detecting system is arranged so that scattered light from a particle on the surface, for example, is collected by a lens array onto a sensor array. The direction of polarization of the parallel light defined by the half waveplate is made substantially parallel to a plane containing optical axes of the illumination system and the detecting system. Thus, even if an error occurs in the angle of incidence of the parallel light upon the reticle, a change in scattered light intensity due to interference between scattered light is kept small to assure accurate discrimination of the particle.