PURPOSE: To constitute a device so that not only pressing of a runner and gate with ejector pins but also direct pressing of a resin part of a molded body by means of a movable core constituting a cavity are performed.

CONSTITUTION: Concentration of stress for mold release only to a gate part is eliminated and the stress for the mold release acts almost evenly on a resin part, a runner and the gate. Consequently, not only peeling of a resin part 20 from a base 18 but also generation of cracks on a part adjoining to the gate of the resin part, through which lowering of yield and reliability in the product can be prevented, are eliminated. Then since it is the movable core 12 itself forming the cavity that presses the resin part directly, such a dent to be obtained in case of pressing with an ejector pin 11 is left behind in the resin part and impairing of external appearance of a molded body is obviated.