A fuel cell system in which fuel cell flooding is eliminated by providing necessary flow speed of fuel gas within a channel while improving system efficiency of the fuel cell by re-circulating unreacted fuel gas, which has been discharged externally from a circulation channel in order to provide the flow speed within the channel. An exhaust gas storage unit which stores exhaust gas is disposed in an exhaust gas recovery channel, to store exhaust gas discharged from the anode channel of the fuel cell. Fuel consumption can be improved by re-supplying the exhaust gas to the fuel cell again. Furthermore, an exhaust storage unit is maintained at a negative pressure. This allows the flow speed of reactant gas flowing through the channel for fuel gas to be increased at the time of opening the control valve connected to the exhaust gas storage unit. Such an arrangement allows water droplets or the like remaining within the anode electrode of the fuel cell to be removed, thereby suppressing flooding. This improves the system efficiency while suppressing fuel consumption.