PURPOSE: To provide a pressurizing method of a gaseous body and the pressurizing device low in equipment cost, high in safety, capable of easily working by anyone without being controlled by High Pressure Gas Regulation Low and particularly suitable for a test or trial for obtaining basic data of high pressure treatment technique using a liquefied gas or a supercritical fluid including extraction, etc.

CONSTITUTION: Carbon dioxide in a polyethylene made bag body 6 is highly pressurized by dipping the bag body 6, in which carbon dioxide is sealed together with a material S to be treated, in water in a pressure vessel 3 and after that, tightly closing the pressure vessel 3 and injecting water under pressure into the pressure vessel 3 by a pressure pump 4.