A method includes arranging and clamping a laminated iron core body between a receive unit and a mold unit that includes a resin pool part, the laminated iron core body including a plurality of laminated iron core pieces and a resin hole pierced in the lamination direction, with the laminated iron core body being clamped, extruding a resin of an inside of the resin pool part using a plunger and injecting the resin into the resin hole, after curing the resin in the resin hole, separating unwanted resin from the plunger by moving the plunger by a given distance in a direction away from the laminated iron core body before the laminated iron core body with unwanted resin is detached from the mold unit, and after separating the unwanted resin from the plunger, moving the plunger to the side of the laminated iron core body.