PURPOSE: To transfer liquid without using a rotary pump and the like by faborably devising arrangement of liquid transfer pipes, and giving pressure difference on liquid levels by gas.

CONSTITUTION: When inert gas is excluded from the upper parts of a first suction pipe 4 and a first vertical pipe 3 as shown with the arrow mark 33, liquid in a tank 2 is brought down in the vertical pipe 3 through the suction pipe 4 and a connecting pipe 5 as shown with the arrow marks 34,35 by pressure difference between the liquid level of the parts and the liquid level in the tank 2, entered to a first liquid feed pipe 1, and reached to a second suction pipe 6. When inert gas in the upper parts of the suction pipe 6, a second vertical pipe 7, a third suction pipe 9, and a third vertical pipe 8 is excluded as shown with the arrow marks 36, 37, pressure on liquid levels of the respective pipes is reduced, and the levels are raised over the liquid level of the tank 2. If degree of reduced pressure of the second suction pipe 6 and the after pipes is equal to or over that of the first suction pipe 4, liquid feed pumps 32b, 32c are smoothly acted, the liquid in the tank 2 can be transferred by flowing in respective suction pipes and vertical pipes as shown with the arrow marks 38, 39, 40, 41, 42.