A fuel cell system comprising: a solid-oxide fuel cell (1, 201); a reformer (2, 202) configured to reform an electric power generation raw material to generate a hydrogen-containing gas and supply the hydrogen-containing gas to an anode of the solid-oxide fuel cell (1, 201); an electric power generation raw material supply unit (5, 205) configured to supply the electric power generation raw material to the reformer (2, 202); a reforming material supply unit (7, 209) configured to supply at least one of reforming water and reforming air, utilized in a reforming reaction, to the reformer (2, 202); an oxidizing gas supply unit (6, 206) configured to supply an oxidizing gas to a cathode of the solid-oxide fuel cell (1, 201); a combustor (3, 210) including an ignitor configured to ignite an exhaust gas discharged from the solid-oxide fuel cell (1, 201); and a controller (8, 208), wherein in an operation stop process of the fuel cell system, which is a process from when an electric power generation stop instruction is received until when the supply of the hydrogen-containing gas and the supply of the oxidizing gas are stopped, the supply of the hydrogen-containing gas and the supply of the oxidizing gas being stopped when a temperature of the solid-oxide fuel cell or a temperature of the reformer reaches a predetermined temperature, the controller (8, 208) is configured to cause the oxidizing gas supply unit (6, 206) to supply the oxidizing gas to the cathode of the solid-oxide fuel cell (1, 201), cause the electric power generation raw material supply unit (5, 205) and the reforming material supply unit (7, 209) to intermittently supply the electric power generation raw material and the at least one of the water and the air to the reformer (2, 202), and cause the ignitor of the combustor (3, 210) to perform an ignition operation, characterized in that the fuel cell system further comprising: a purifier (16, 231) provided downstream of the combustor (3, 210) to purify a combustible gas contained in a flue gas discharged from the combustor (3, 210); and a purifier temperature detecting portion (T4, T40) configured to detect a temperature of the purifier (16, 23) as a temperature detecting portion configured to detect a temperature of the fuel cell system, wherein when a detection result of the purifier temperature detecting portion (T4, T40) is less than a predetermined temperature, the controller (8, 208) is configured to cause the ignitor to perform the ignition operation. a solid-oxide fuel cell (1, 201); a reformer (2, 202) configured to reform an electric power generation raw material to generate a hydrogen-containing gas and supply the hydrogen-containing gas to an anode of the solid-oxide fuel cell (1, 201); an electric power generation raw material supply unit (5, 205) configured to supply the electric power generation raw material to the reformer (2, 202); a reforming material supply unit (7, 209) configured to supply at least one of reforming water and reforming air, utilized in a reforming reaction, to the reformer (2, 202); an oxidizing gas supply unit (6, 206) configured to supply an oxidizing gas to a cathode of the solid-oxide fuel cell (1, 201); a combustor (3, 210) including an ignitor configured to ignite an exhaust gas discharged from the solid-oxide fuel cell (1, 201); and a controller (8, 208), wherein in an operation stop process of the fuel cell system, which is a process from when an electric power generation stop instruction is received until when the supply of the hydrogen-containing gas and the supply of the oxidizing gas are stopped, the supply of the hydrogen-containing gas and the supply of the oxidizing gas being stopped when a temperature of the solid-oxide fuel cell or a temperature of the reformer reaches a predetermined temperature, the controller (8, 208) is configured to cause the oxidizing gas supply unit (6, 206) to supply the oxidizing gas to the cathode of the solid-oxide fuel cell (1, 201), cause the electric power generation raw material supply unit (5, 205) and the reforming material supply unit (7, 209) to intermittently supply the electric power generation raw material and the at least one of the water and the air to the reformer (2, 202), and cause the ignitor of the combustor (3, 210) to perform an ignition operation, a purifier (16, 231) provided downstream of the combustor (3, 210) to purify a combustible gas contained in a flue gas discharged from the combustor (3, 210); and a purifier temperature detecting portion (T4, T40) configured to detect a temperature of the purifier (16, 23) as a temperature detecting portion configured to detect a temperature of the fuel cell system, wherein when a detection result of the purifier temperature detecting portion (T4, T40) is less than a predetermined temperature, the controller (8, 208) is configured to cause the ignitor to perform the ignition operation.