To enable effectively separating gas and liquid under minute gravity environment such as within a spaceship by housing a rotor whose upper part is partially opened in a closed vessel, introducing liquid that gas and liquid coexist inside the rotor through a line, and separating it into liquid and gas by a difference in mass.

Liquid 6 that gas and liquid coexist in a storage tank 600 is introduced into a closed vessel 1 by a conveying function 7. In this vessel 1, a rotor 2 whose upper part is partially opened is housed, and the liquid 6 is directed and discharged to the upper part or the side face of the rotor 2 from the bent tip part of a line 22. At this time, the liquid 6 under minute gravity environment and in a state in which it does not receive centrifugal force is moved toward the upper part or the side face of the rotor 2 by inertial force, and the moving velocity of liquid is by far higher than that of gas by a difference in mass between liquid and gas, and it comes into contact with the upper part or the side face of the rotor 2 and is accumulated on the side face of the rotor 2. On the other hand, gas is left alone near the tip part of the line 22 and is discharged from a line 23 through a separation membrane 15.