A movable mold is movable toward and away from a fixed mold so as to close and open the mold. The fixed mold includes an intermediate plate facing a movable-side mold plate. This intermediate plate has a retainer-molding recess which cooperates with the movable-side mold plate to form a retainer-molding cavity, and a core pin, which cooperates with a housing-molding recess to form a housing-molding cavity, is mounted on the intermediate plate. A retainer, molded in the molding cavity, is moved downward by an ejector pin into a position where the retainer is disposed coaxial with a housing. Then, the two molds are again closed together, so that the housing and the retainer are connected together, and then this assembled product is taken out.