A method and apparatus for manufacturing pressurized packages capable of obtaining gas displacement pressurized canned goods with high accuracy of internal pressure by atomizing liquid nitrogen, and supplying it together with low temperature vaporized gases to a head space of a can. A spray device assembly (10) for atomizing and spraying the liquid nitrogen is provided in an opening of the bottom of a liquefied gas storage tank (1) formed as a vacuum heat insulating structure. The spray device assembly (10) is constituted such that a valve (2) for controlling the flow rate of liquid nitrogen, a spray nozzle (3), a liquid nitrogen flowpassage (4) extending from the valve (2) to the spray nozzle (3), a nozzle cooling tank (5) for cooling the flowpassage, and a purge device for cutting an outer peripheral portion of a nozzle and an outlet portion off from the air, so as to prevent them from being frosted, are integrally mounted on a spray body 6. The nozzle cooling tank (5) always cools the pipe 13 and the nozzle 3 by liquid nitrogen, and enables supplying of the liquid nitrogen to the nozzle having a temperature gradient to the neighborhood of a boiling point, without boiling and vaporizing it from the tank to the nozzle. The liquid nitrogen supplied while preventing of being vaporized to an orifice inlet of the spray nozzle allows to pass through a nozzle orifice in the liquid state to release into the atmosphere, thereby giving rise to a rapid vaporizing expansion immediately after moving out of the nozzle orifice, so that other liquid nitrogen still in the liquid phase state is atomized.