An authentication apparatus includes a prism, an imaging unit, and a visible light source configured to radiate a visible light to a living body. The prism comprises: a contact surface configured to be in contact with the living body a reflection surface configured to be in contact with the contact surface, and totally reflect light from a concave portion of the living body and light from a convex portion of the living body and an imaging surface configured to be opposed to the contact surface, in contact with the reflection surface, and provided at an angle such that the light from the concave portion of the living body cannot be reached, and the light totally reflected by the reflection surface and the light from the convex portion of the living body can be transmitted. The imaging unit images the light which is transmitted through the imaging surface.
