To minimize the coupling loss even in a case of an optical fiber having a large core diameter by interposing an optical guide body, which has an optical guide path surrounded with a reflecting surface of high reflectivity, between the optical fiber and the light receiver element.

An optical guide body 1 is formed into a tapered, hollow, cylindrical shape getting narrower toward the tip using, for example, a metal material and a plastic material. The internal circumferential face for surrounding an optical guide path 2 therein is turned into a silver surfacing by being treated its surface by silver and aluminium so as to become a reflecting surface 3 having high reflectivity. This optical guide body 1 is closely interposed between an optical fiber 4 and an light receiver element 5. That is to say, the large-diameter side of the optical guide path 2 is brought in close contact with an outgoing end of the optical fiber 4 and the small- diameter side of the optical guide path 2 is brought in close contact with the light receiver surface of the light receiver element 5 so as to be interposed between the optical fiber 4 and the light receiver element 5. The light outgoing from the optical fiber 4 is incident in the optical guide path 2 of the optical guide body 1 and in the optical guide path 2, the light is collectively guided to the light receiver element 5 by repetition of the reflection of the reflecting surface 3 having high reflectivity.