A light isolator member of an embodiment of the present invention is configured to be joined to another light isolator member to serve as a part of a light isolator, the light isolator member including: a lens surface disposed in a first surface; a transmission surface disposed at a position corresponding to the lens surface in a second surface on a side opposite to the first surface; and a fitting part disposed in the second surface, the fitting part being configured for fitting to the other light isolator member.