This paper proposes a power-leveling method in which a lithium-ion battery and a flywheel energy storage are installed in a photovoltaic power generation plant. The proposed method is a division method that focuses on the amplitude component of the compensating power required to level the generated power of photovoltaic power generation. Furthermore, by adding the flywheel state-of-charge automatic adjustment method to the proposed method, the coverage period of the flywheel is improved. The effectiveness of the proposed method is verified on an actual 40 kW plant.