An imaging device includes: a sensor unit that is arranged at a predetermined position inside a casing, and that images a subject outside the casing through an opening portion, with a part of an imaging region, while imaging a reference chart with another part of the imaging region; and a light absorption member that is arranged in an optical path of light from a illumination light source toward a specular-reflection position from which specular-reflection light of the illumination light source is entered to the sensor unit, in the imaging range. The light absorption member has at least a first surface on which light from the illumination light source toward the specular-reflection position is irradiated, and a second surface that faces to the first surface, and reflected light that has been reflected on the first surface and then on the second surface is further directed toward the first surface.