An authentication apparatus includes a prism and an imaging unit. The prism comprises: a contact surface, an imaging surface, a first reflection surface opposed to the imaging surface, contacted with the contact surface to make an angle to be lower than an optimum angle to an incident light from a concave portion of the living body, and to reflect an incident light from a convex portion of the living body on the imaging surface and a second reflection surface opposed to the imaging surface, contacted with the first reflection surface, and to form a reflection body that reflects the incident light from the concave portion of the living body and the incident light from the convex portion of the living body on the imaging surface. The imaging unit images the light which is reflected by the first reflection surface and the light, which is reflected by the second reflection surface.
