A power generation apparatus that suppress cavitation includes a first on/off valve provided between a steam generator and an expander in a circulating channel; a bypass channel connected between an area between the steam generator and the first on/off valve and an area between the expander and a condenser; a second on/off valve provided in the bypass channel; a third on/off valve provided between a pump and the steam generator; and a controller. When stopping the pump, the controller outputs a control signal that stops the pump, a control signal that closes the first on/off valve, a control signal that opens the second on/off valve, and a control signal that closes the third on/off valve. In the case where a predetermined condition has been met, the controller outputs a control signal that closes the second on/off valve.