To provide a clean buoyancy-utilized pumping type hydraulic power generating set having little energy consumption without receiving various constraints such as environment and location.

A lift type opening/closing valve 12 is fitted to a measure-like bucket 1, it is fitted to a highly-airtight bag-like balloon 2 fitted with a release port opening/closing valve 17 by a tie 16, and the balloon 2 is fitted to guide rails 3. Two guide rails 3 are faced each other, and they are separated at the upper and lower ends to form two semicircular loops. An intake pipe 9 and a discharge vent pipe 10 are connected to an air pump 15, and hydrogen gas is filled in them. A hydrogen gas tank 14 for supplying gas and an injection pipe 11 are connected to the vent pipe 10, and expansion port opening/closing valves are fitted to the pipes. An opened receiving channel 4 is installed on the upper end side of the guide rails 3, an upper pool 5 and a surge tank 13 are connected on the downstream side of the receiving channel 4, and a water drop pipe is connected on the downstream side of them. A power generator 8 is installed via a water control valve 19, and a lower pool 6 is installed on its downstream side.