To provide a mold and method for molding a resin, capable of easily performing the gate cutting work of a resin product.

In the mold 10 for molding a resin, a disc blade cutting device for molding the resin product 22 having the shape of a cavity part 20 by injecting a thermoplastic resin material 12 in the cavity part 20 in a flowable state from the injection route 14 through a runner 16 and a sump part 18 is constituted of a positioning means 16 for positioning the disc blade of a mower 12 and a grinder 20 for rotating a cutting grindstone 18.