PURPOSE: To reduce the working time by a linear resin material is melted being fed sequentially into a melting cylinder attached to an injection molding machine and sent into an injection cylinder by a required amount to perform an injection molding.

CONSTITUTION: A linear resin molding material 20 wound around a bobbin 21 passes through a melting cylinder 10 with an infrared lamp 9 and transferred into an injection cylinder 12 from a passage 17a at the tip thereof 12. The melted resin molding material transferred into the injection cylinder 12 is injected into a die from a nozzle 14 with a plunger 13 thereof 12 and molded. This enables the melting of the resin material for injection molding sequentially by an amount required for molding thereby reducing the required time for starting molding.