PURPOSE: To remove the periodical fluctuation of a wave power generating output which is based on the periodical property of the energy of wave power by a method wherein a hydraulic motor is connected with an accumulator.

CONSTITUTION: In case a pendulum 107 is swung by the wave power and a cylinder 110 is being driven, oil discharged out of the cylinder 110 flows to the hydraulic motor 121a and the accumulator 125a simultaneously when a piston 110a is being shifted to the left. When the piston 110a is moved to the right, the discharged oil from the cylinder 110 flows to the hydraulic motor 121b and the accumulator 125b. Accordingly, a generator is driven for this period by the hydraulic motor 121b instead of the same 121a, however, the hydraulic motor 121a drives the generator successively for a period of time in which the oil in the accumulator 125a is being discharged.