Provided is a power generation system capable of generating power using natural energy such as water power or wind power by being installed at a river, a waterway, a coast, a windy place, or the like. A power generation system 1 according to the present invention includes a turbine 2, a cam wheel device 6, a power generator 7, and an arm mechanism 8. The turbine 2 is provided with a rotary shaft 11 which is rotated by water power or wind power applied thereto. In the cam wheel device 6, a cam wheel 18 is rotated by torque being transmitted from the rotary shaft 11 to the cam wheel 18. In the power generator 7, a rotary shaft 28 is rotated by rotation of a driving wheel 29, the rotation energy of the rotary shaft 28 is converted to electrical energy, so that power can be generated. By rotation of the cam wheel 18, the cam 21 comes into contact with the arm mechanism 8, and thus, the arm mechanism 8 is turned. By being turned, the arm mechanism 8 comes into contact with the driving wheel 29, and thus, the driving wheel 29 is rotated.