PURPOSE: To provide a gate cutter also ejecting a molded form by a gate cut pin in the perforated molded form.

CONSTITUTION: A slidable gate cutter with a gate end section 31 forming a gate G together with a sprue bush 20 while being positioned in the sprue bush 20 at the position of the hole of a molded form, a gate cut section 32 formed continuously in size larger than the end section 31, and a discharging section 33 continued to the gate cut section 32 and formed in size larger than the hole is used as a gate cutter S in an injection molding die. The gate cutter S is composed of structure, in which a gate is cut by the gate cut section 32 after injection while the cut-pin tip section 31 is abutted against an engaging surface 20b as the base of the sprue bush 20, and a fixed quantity of the discharging section is projected to the outside of the mold after the mold is opened.