A power generation system of the present invention includes: a fuel cell unit (101) including a fuel cell (11) and a case (12); a controller (102); a combustion unit (103) provided outside the case (12) and configured to combust a combustible gas to supply heat; and a discharge passage (70) configured to cause the fuel cell unit (101) and the combustion unit (103) to communicate with each other, wherein in a case where an exhaust gas is being discharged to the discharge passage (70) from one of the fuel cell unit (101) and the combustion unit (103) and the controller (102) changes the flow rate of the exhaust gas discharged from the other unit, the controller (102) controls at least the flow rate of the exhaust gas discharged from the other unit such that the flow rate of the exhaust gas discharged from the one unit becomes constant.