A power generation apparatus comprising: a steam generation means that evaporates a liquid working medium by heating the working medium using a thermal medium; an expander that expands the gaseous working medium and produces power as a result; a condensing means that condenses the gaseous working medium by cooling the working medium using a coolant medium; a pump that circulates the working medium; a closed-loop circulating channel in which said steam generation means, said expander, said condensing means, and said pump are connected in series; a first on/off valve provided in said circulating channel between said steam generation means and said expander; a bypass channel connected between an area in said circulating channel between said steam generation means and said first on/off valve and an area between said expander and said condensing means; a second on/off valve provided in said bypass channel; a third on/off valve provided in said circulating channel between said pump and said steam generation means; and a control means that is adapted to carry out control for starting and stopping said pump and opening and closing said on/off valves (11, 12, 13), characterized in that when stopping said pump, said control means is adapted to output a control signal that stops said pump, a control signal that closes said first on/off valve, a control signal that opens said second on/off valve, and a control signal that closes said third on/off valve, and then, in the case where a predetermined condition has been met, the control means is adapted to output a control signal that closes said second on/off valve. a steam generation means that evaporates a liquid working medium by heating the working medium using a thermal medium; an expander that expands the gaseous working medium and produces power as a result; a condensing means that condenses the gaseous working medium by cooling the working medium using a coolant medium; a pump that circulates the working medium; a closed-loop circulating channel in which said steam generation means, said expander, said condensing means, and said pump are connected in series; a first on/off valve provided in said circulating channel between said steam generation means and said expander; a bypass channel connected between an area in said circulating channel between said steam generation means and said first on/off valve and an area between said expander and said condensing means; a second on/off valve provided in said bypass channel; a third on/off valve provided in said circulating channel between said pump and said steam generation means; and a control means that is adapted to carry out control for starting and stopping said pump and opening and closing said on/off valves (11, 12, 13), characterized in that when stopping said pump, said control means is adapted to output a control signal that stops said pump, a control signal that closes said first on/off valve, a control signal that opens said second on/off valve, and a control signal that closes said third on/off valve, and then, in the case where a predetermined condition has been met, the control means is adapted to output a control signal that closes said second on/off valve.