PURPOSE: To prevent the malfunction of a received signal even if electromagnetic noises of high electric field intensity are radiated by connecting metallic sleeves to the ground potential of an electric device.

CONSTITUTION: A contactor 13 which is electrically connected with a metallic fitting 6 for building metallic sleeves 3, 3' into a housing 5 is so provided on the outer side of the housing 5 of the optical connector as to project onto a male part 4 side of an insertion guide and further, a contactor 14 which is electrically connected to the contactor 15 is provided on the outer side of a housing 10 of the light transmission module. The contactor 13 of the optical connector comes into contact with the contactor 14 on the light transmission module side simultaneously when the optical connector and the light transmission module are inserted and connected. The contactor 14 is connected to the reference potential, for example, the ground potential on the electric device side. Then, the metallic sleeve 3 serves as an antenna when the electromagnetic noises of the high electric field intensity are radiated. The electromagnetic noises flow to the metallic fitting 6 → the contactor 13 → the contactor 14 →the ground potential even if these noises are absorbed. The generation of an induction voltage is thus obviated.