PURPOSE: To easily manufacture a wave force pump even when the pump is upsized by transmitting the power of a float oscillating by the wave force to a piston In an oscillatable cylinder provided underwater through a chain and a piston rod to allow the water inside the cylinder to be discharge/enter through a U-shaped tube.

CONSTITUTION: When a float 17 on the sea surface falls by the wave, a piston 12 at the sea bottom falls by the effect of a weight 25. Then, water is sucked into a cylinder 1 through a suction strainer 23, a non-return valve 22, a tube 14, a joint ring 8, a nozzle projecting outwardly of the joint ring 8, upper and lower elbows 6, 6" of a U-shaped tube 6, a nozzle 5, etc. The nozzle projecting outwardly of the joint ring 8 is inserted in the U-shaped tube 6. When the float 17 is made afloat with the wave, the piston 12 in the cylinder 1 is also made afloat, and the water in the cylinder 1 is pressurized and discharged from a tube 24 by the effect of the non-return valve 22.