A process for optically joining a plurality of optical fibers to an opponent member, comprising the steps of forming an optical fiber array by fixing the optical fibers between a V-grooved base plate and a fixing base plate in the state that the optical fibers are fitted to respective V-grooves formed on a surface of the V-grooved base plate, and optically joining the optical fibers of the optical fiber array to the opponent member by using, as a joining reference surface, either one of a first surface of the fixing base plate at which the optical fibers are fixed and a second surface of the fixing base plate opposite to said surface.