To minimize the discharge amount of a battery, while obtaining power by moving a motor with electric power of the battery without using an engine.

A flywheel (1), as well as, an electric motor (6), a motor generator (5), and the battery (20) for extracting its characteristics are used. The motor generator (5) is used as a power generation function and motor power. Rotative power is obtained, by making the flywheel (1) rotate on a center shaft (2) which does not rotate, using the belt (8) drive of the electric motor (6) and a motor of the motor generator (5), and the power is transmitted to an external machine by a transmission part (7).