To provide a power generation system effective, inexpensive, and low in environmental load.

A towing tool is attached to livestock suitable for carrying heavy articles, such as cattle, a horse, a donkey, a mule, a camel or an elephant, the towing tool and a rotary shaft are connected by an arm extending in parallel to the ground, an electric conversion device such as a speed-up gear mounted on an automobile or a bicycle to increase the speed of rotation transmitted from the arm, a generator, an inverter or a converter is provided, and muscular strength of the livestock is converted into the electric power by the generator in such the feeling like grinding powders with a stone mill.