A prism member of an authentication apparatus includes a living body contact surface configured to be in contact with the living body, and an imaging surface opposed to the living body contact surface and formed at a position generally parallel therewith. The prism member includes a reflection surface in contact with the living body contact surface and the imaging surface, to totally reflect light reflected from the former surface toward the latter surface. The reflection surface is at angle such that (i) light through the living body contact surface into the prism member does not reach to the reflection surface, and (ii) light from an inside of the prism member is totally reflected at the living body contact surface in an optical path running from the imaging surface and reaching the living body contact surface by way of the reflection surface. A first imaging unit captures a living-body reflected light.