Fuel cell system

The fuel cell system (F1) is equipped with a fuel cell (10) for generating power by chemically reacting a fuel gas supplied to an anode (11) and an oxygen containing gas supplied to a cathode (12); an anode off-gas discharge mechanism (54) for discharging an anode off-gas from the anode; a combustion heater (51) for combusting a combustion gas; a dilution mechanism (71) for diluting the anode off-gas by the oxygen containing gas; a first path (67) for introducing the anode off-gas into the combustion heater; a first flow rate adjustment mechanism (54) for adjusting an introduction amount of the anode off-gas into the first path; a second path (79) for introducing the anode off-gas into the dilution mechanism; a second flow rate adjustment mechanism (72) for adjusting an introduction amount of the anode off-gas into the second path; and a control mechanism (90) for controlling actuations of the first flow rate adjustment mechanism and the second flow rate adjustment mechanism.