Abstract: A gas-feeding device as follows:(A) a gas-feeding nozzle and(B) gas-feeding nozzle shifting device for putting a top portion of the gas-feeding nozzle in forward and backward movement in a guide portion which is provided in a mold and communicates with a cavity and an outside of the mold,the gas-feeding device being used for feeding a pressurized gas through the gas-feeding nozzle into a molten resin injected into the cavity of the mold attached to an injection molding machine for producing a molded article having a hollow portion,wherein:a clearance is provided between the top portion of the gas-feeding nozzle and the guide portion, andat least part of the top portion of the gas-feeding nozzle is out of contact with the guide portion when the molten resin is injected into the cavity.