To enable connectebility between a mounting member and a cover to be guaranteed perfectly by forming a mounting part integrally on the cover via a thermally fused layer continuing to the inner surface of a hole and to the cover the outer surface continuing to the inner surface of the hole by injecting a hard resin on the second cavity.

The seventh die 64 is provided with plural pin-like parts 67 whose top parts are inserted in a punching hole 65 by advancing to/retiring from the punching hole 65. An air supply port 68 continuing to an action space 63 is provided on a movable side die plate. When pressurized air is supplied from the air supply port 68 to the action space 63, the seventh dies 64 are advanced and stopped at their set positions by means of the third stopper 71. The second die 62 is composed again as the second die by advance of the seventh die 64. The punching hole 65 is filled by the top head parts of the pin-like parts 67. The first cavity 10 is formed by means of the first die 61, the second die 62, the fourth die 14 and a die part 23. And resin is introduced from the first gate 9 to form a cover.