PURPOSE: To prevent the swallowing up bubbles, deformation of lead frame and metallic wires from occurring by a method wherein a movable part to control resin fluidization is retractively provided in a cavity of a resin sealing dies.

CONSTITUTION: A cavity 106 in top and bottom dies 103, 104 is filled with sealing resin 107. A flow control pin 105 projecting into the bottom die 104 narrows the flow path of resin in the bottom die 104 to restrict the resin filling-in speed in the bottom die 104. On the contrary, the resin filling-in speed in the top die 103 not restricted at all accelerates the resin fluidization in the upper part of the cavity 106 to level off the resin fluidization in the upper and lower parts in the cavity 106. The nearer the time point to the termination of the resin filling-in process, the lower the flow control pin 105 is shifted to increase the feed of sealing resin 107 so that the cavity 106 in top and bottom dies 103, 104 may be completely filled with the resin 107 to be resin-molded in specified shape by taking the flow control pin 105 out of the cavity 106 of the bottom die 104.