The catalytic combustor is configured to accelerate the combustion processing of anode off gas in the combustor in order to reduce the amount of unburned hydrogen discharged to the outside the combustor. The anode off gas and cathode off gas discharged from the fuel cell (1) is fed into the catalyst combustor 25 is burned by use of a catalyst (29). Ventilation air is supplied into the fuel cell 1 is supplied to as a catalytic combustor (25). Portion of the catalyst combustor (25) positioned in the catalyst 29 upstream of the internal divider plate 35 is divided into the upper flow path 37 and the lower flow passage 39 by the gas flow into 33 the upper and lower flow path is provided upstream of the (37, 39). Cathode exhaust gas is fed to the gas flow (33). A catalytic combustor, a fuel cell, the anode off gas, cathode off gas, ventilation air