To provide a generator capable of providing power generation force higher than additional electric power required for external power, in a power generation system capable of generating electric power even in any place on the earth when power generation can be performed by using gravity, and converting constant swing motion (pendulum motion) of using the gravity and inertia force by artificially adding small assisting force from an external part, into rotary motion.

A dropping speed is enhanced by adding external force (for example, driving for several seconds by connecting an electric motor) in the vicinity where a weight of a swing type driving device attached with the weight of proper weight of installing a unidirectional driving free hub, becomes a maximum dropping speed. A flywheel attached with the unidirectional driving free hub is rotated at a high speed by a rotary belt (or a chain) for converting its swing (pendulum) motion into the rotary motion, and high speed rotation energy provided by its torque by further changing the gear ratio, is transmitted to a generator. An electric power source of an acceleration motor required for adding the external force, can generate electric power even in any place on the earth when charging a part of external electric power and self-power generation to a battery.