PURPOSE: To handle pure water with contact with outdoor air being cut off and with high purity being maintained by taking measures for a gas-liquid storage tank, such as the arrangement of an evacuating means, a pure water feeding means. an inert gas feeding means, and a pure water takeout means.

CONSTITUTION: When a device body 1 is operated, first a stop valve V0-A is opened, and a three-way valve V1 is opened to the 1st branch passage 15A side, and also a suction pump 16 is operated. And inert gas G in a gas-liquid storage tank 2 is sucked to evacuate the tank. At this time, a stop valve V0-B is opened and a three-way valve V2 is opened to the 1st branch passage 19A side to suck pure water W in a pure water feeding tank 20 into the gas-liquid storage tank 2, allowing it to be stored in a gas-liquid housing chamber 5. And the stop valve V0-A is opened and the three-way valve V1 is opened to the 2nd branch passage 15B side to deliver inert gas in a cylinder 17 into the gas-liquid storage tank 2 to pressurize it. Further, the pure water W in the gas-liquid storage tank 2 is taken out into a test tank T through passage means 23, 19, 19B.