A condenser condenses an unused exhaust gas exhausted from a fuel cell and recovers water, condensation-capacity detection means always monitors the condensation capacity of the condenser, control means controls an output of heat-transport-medium circulation means, stores the exhaust heat of the fuel cell in heat-using means when a sufficient condensation capacity is left, and stops the heat-transport-medium circulation means to complete exhaust-heat recovery when the condensation capacity lowers. Moreover, a fuel cell, a cooling pipe through which a first heating medium of carrying the heat of the fuel cell circulates, a cooling-water pump of circulating the first heating medium, and a fuel-cell-temperature detector of detecting the temperature of the fuel cell are used to operate a cooling-water pump until the temperature detected by the fuel-cell-temperature detector becomes a predetermine threshold value or less even after supply of a fuel and an oxidant to the fuel cell is stopped.