FUEL CELL SYSTEM

A control unit of a fuel cell (i) performs, when an estimated value of a storage amount in a storage portion of a gas-liquid separator is larger than a threshold storage amount, a first calculation process of calculating an estimated value of a discharge amount after a drain valve is opened, based on a drain speed which is determined with respect to a differential pressure in a first relationship; and (ii) performs, when the estimated value of the storage amount is equal to or smaller than the threshold storage amount, a second calculation process of calculating the estimated value of the discharge amount, based on a current drain speed determined with respect to an estimated value of a current storage amount in a second relationship that is prepared in advance and in which the drain speed decreases as the estimated value of the storage amount decreases.