To provide a safe power generation means not polluting the environment.

Pump type water tanks 1, 2 are arranged under ground of a tollgate of an expressway, a seesaw plate is put on the same and assist plates 5, 6 for relaxing a step at a time of enter of an automobile are provided. The pump type water tanks 1, 2 are connected by two conduits 13, 14 provided with valves 9, 10, 11, 12. When the automobile drives on the pump type water tank 1, water flows in the conduit 13 through the valve 9 to rotate a power generation turbine 3 and empty pump type water tank 2 is filled with the water. When the automobile moves to the pump type water tank 2, water flows reversely to rotate the power generation turbine 3 and heads for the pump type water tank 1.