In order to provide a discriminating device in which high discrimination accuracy is achieved by appropriately setting parallelism of a plurality of light beams caused to enter a recording material, provided is a discriminating device including: a light guiding member configured to guide a plurality of light beams from a light source to an irradiated surface; an image pickup element configured to receive a light beam from the irradiated surface; and an optical system configured to guide the light beam from the irradiated surface to the image pickup element, wherein the plurality of light beams include a plurality of first light beams which are emitted from the light guiding member and enter a first effective region of the irradiated surface, and wherein the plurality of first light beams form an angle of 7° or less with each other within a first cross section parallel to the irradiated surface.