PURPOSE: To remove the trace of the cut-off of the gate section of a molded form by a method wherein an inserting hole bored at a position corresponding to the end face of the molded form in a mold cavity is formed, a gate is bored to the inserting hole, a resin is injected and an opening surface on the cavity side and the gate are closed by a slide block.

CONSTITUTION: An inserting hole 37 bored at a position corresponding to the end face of a molded form in a cavity 36 is formed to a template 23 demarcating the cavity 36. A slide block 25 is inserted slidingly into the inserting hole 37. A gate 45 is bored near the cavity-side opening surface 39a of the inserting hole 37. A molten resin is injected, and the slide block 25 is moved before the resin in the cavity 36 is solidified, and the cavity-side opening surface 39a and the gate 45 are closed. The resin in the cavity 36 and the resin in the gate 45 are separated completely, thus eliminating the need for the cut-off process of the gate section, then also leaving no cut-off trace.