PURPOSE: To get a high head in a simple structure.

CONSTITUTION: An air delivery hose 12 connected to the delivery outlet of a compressor 20 is contained in an air-lift hose 13 so as to extend to the lower end along the longitudinal direction of the hose to constitute a double-tube. The underground water which rises in the air-lift hose 13 is conducted to a water tank 21 installed on the ground. A part of the double-tube is positioned deeper than the underground water level in a well 1 and compressed air supplied from a compressor 20 is ejected into the air-lift hose 13 from the lower end of the air delivery hose 12 to lift up the underground water filled in the air-lift hose 13.