To utilize water buoyancy.

While water is mechanically poured into water tanks 1, 2, and floats 5, 6 are made to rise with floating weights by means of generation of buoyancy in the floats 5, 6, the floats 5, 6 supply energy to an outside while increasing self internal energy. The water tanks 1, 2 are filled with water, the weights 5, 6 are laid on the water, thereby discharging the water. The tanks 1, 2 from which the water is discharged become vacant. While increasing self internal energy by dropping the floating weights from an upper space of the vacant water tanks 1, 2, the energy is supplied to an output shaft 20. In this manner, the floats 5, 6 rise with the floating weights by means of buoyancy generated by pouring water in the tanks 1, 2 in which the floats are repeatedly fall into their bottoms, and supply energy to the outside while increasing its internal energy. By alternately repeating this method, mechanical power is generated.