To solve the problems such that a resin pellet is deteriorated by hydrolysis due to moisture or oxidation due to silver and oxygen by intermolecular moisture, intermolecular oxygen or atmospheric oxygen; and the moisture contained in the air possibly causes a dry-returning phenomenon increasing the moisture again since the air is taken in by a second blower for transporting the resin pellet to a loader on machine, when melting the resin pellet with a resin molding machine such as an injection molding machine to be used, though the moisture attached to the surface of the resin pellet is dried by dehumidifying it by sending in heated air.

In the method of supplying nitrogen gas in the resin molding machine 310 constituted of a material supply system for supplying a dried resin pellet 201 and a plasticizing cylinder 311 for melting the resin pellet 201, the intervention of air at all the places is excluded by supplying nitrogen gas while heightening the purity of the nitrogen to be supplied to the plasticizing cylinder 311 to be higher than the purity of the nitrogen supplied to the material supply system.