To obtain buoyancy type power, while efficiently rotating and driving a hydraulic turbine by adopting pumping water pressure generated due to buoyancy.

A power generating hydraulic turbine 6 is connected to the upper opening side of a pipe-like water tank 1 via a guide pipe 4. A water charging valve port 7 is formed on an upper side wall surface of the water tank 1. A hydraulic pressure sensor 8 is arranged on a lower sidewall surface of the water tank 1, for closing the water charging valve port 7 by sensing prescribed hydraulic pressure in the water tank 1. A floating body 2 is sunk in the water of tank 1, while floating due to its own buoyancy for generating the hydraulic pressure. A traction means 3 is attached to the water tank 1, in which one end of a traction wire 9 is pulled outside the water tank 1 through a hose 11 connected to a lower side inside the water tank 1 for the traction of the float 2 to the lower side inside the water tank 1, and the other end is connected to a wire-winding machine 10.