PURPOSE: To avoid the trouble due to the cooling of a gate position when precision molding is performed by low speed injection molding by providing a core mold constituting a cavity and a vibrator vibrating the cavity surface of the core mold to a mold and operating the vibrator from the time of the injection of a resin to the time of the completion of filling or cooling.

CONSTITUTION: A core mold 9 is fitted in the space 20 between a fixed template and a movable template and a cavity 12 is formed to the core mold 9. Vibrators 22a-22c are integrally provided to the core mold 9. Connection parts 24 are formed at positions where the fixed and movable templates come into contact with the vibrators 22a, 22b and connected to the operation means of the vibrators by lead wires 26. When a resin is injected and the core mold 9 is vibrated, the resin being in contact with the surface of the cavcity internally generates heat and flows in the cavity with good flowability.