In a discriminating apparatus, a substrate portion of printed matter is irradiated with a light beam emitted from a light source, and the intensity of the light beam reflected from the substrate is detected by a photodetector. The discrimination as to whether the printed matter is the original or a reproduction is performed by a discriminating unit based on the contrast value in the intensity of the reflected light detected by the photodetector. Thus, the discriminating apparatus discriminates whether the printed matter is the original or a reproduction at high speed and also permits lowering the possibility of an erroneous discrimination.