A power generation system includes: an air intake passage; a fuel cell system that includes a fuel cell; a case configured to house the fuel cell, a ventilator (air supply unit), and an air intake temperature detector configured to detect a temperature of the intake air supplied to the case; a combustion device that includes a combustor; an exhaust gas passage configured to discharge a flue gas generated in the combustion device to the outside; and a controller. The air intake passage and the exhaust gas passage are configured to allow heat exchange to occur between media flowing through the passages. The controller causes the combustion device to operate when the fuel cell system is activated and the temperature detected by the air intake temperature detector is equal to or lower than a first predetermined temperature.