The optical object discriminating device includes a light projecting part which applies light, which is emitted from a semiconductor light emitting element, to a measuring object which is an object to be measured, and a light receiving part which receives reflected light reflected by the measuring object. Between the light receiving part and the measuring object is placed a polarization-state selector part which permits polarized light of a specified polarization direction to pass therethrough. A signal processing part processes a signal outputted by the light receiving part, and measures intensity of light of the polarization direction permitted by the polarization-state selector part to pass therethrough.