PURPOSE: To protect a ferrule, to disuse an optical relay adapter in the case of connection, to hold the connection state of the optical fiber on an optical axis and to facilitate the connecting work of an optical connector by mutually fitting, locking and fixing the optical connectors having the same shape.

CONSTITUTION: Coated optical fibers 1A and 1B are held by the ferrules 2A and 2B. In the case of connecting the optical fiber by using the optical connector, the engaging piece projected parts 3A and 3B of the optical connector are engaged along the engaging piece recessed parts 4A and 4B of the other optical connector, the end faces of the ferrules 2A and 2B, that is, the end faces of the coated optical fibers 1A and 1B are butted while they are aligned on the optical axis. Furthermore, square holes 6A and 6B formed on lock housings 8A and 8B are fitted out the projections 7A and 7B formed on the lock housings 8A and 8B of the other optical connector. As a result, the optical fiber is aligned on the optical axis and the accurate and firm connection of the optical connector is completed.