PURPOSE: To balance flows of molding material and consequently prevent void and the like from developing within a molded part by a method wherein members to control the flows of molding material in a cavity are protruded at the early stage of pouring of the molding material.

CONSTITUTION: Ejector pins 10 are protruded in a cavity 3 at the early stage of pouring of high viscous molding material into the cavity 3. As a result, the flow passage resistance is increased by the ejector pin 10 near the spouting port of a gate 4, resulting in reducing the flow speed and lowering the pressure and the like of the molding material flowed from the gate 4 in the lower space of the cavity 3. Because the flows of the molding material are controlled as mentioned above, the flow of the molding material in the lower space balances with that in the upper space of the cavity 3. Accordingly, the development of void and the deformation of a lead frame and the like, all of which are caused by the unbalance between the flows of molding material, are prevented from occurring.