To provide a technology for carrying out high reliable gate cut without applying an unreasonable load on a mold for mold resin injection molding while many of injection molding two-plate mold structures adopting side gate systems have problems that a molded article, and a sprue and a runner being unnecessary portions are discharged from the mold in a connected state, and after that, a step of separating the molded article from the sprue and runner performed manually or by using a robot is necessary in order to cut the gate.

In the two-plate mold structure adopting the side gate 9 system of the mold for mold resin injection molding, the sprue 12 and the runner 13 are separated from the molded article by incorporating a sprue bush and a rotary sleeve 2 rotatable in the center axis direction of the sprue bush, and rotating the rotary sleeve in which a gate groove 16 is formed at a runner groove 10 of a fixed sprue bush to block a flow path to a molding part.