A fuel cell system performs feedback control with respect to a reactive gas supplying apparatus based on a proportional obtained by multiplying a deviation of an actual flow quantity from a target value of a reactive gas supplied to the fuel cell from the reactive gas supplying apparatus by a proportional gain and an integral term obtained by multiplying the deviation by an integration gain to perform time integration in such a manner that the actual flow quantity coincides with the target value, and changes an update arithmetic operation of the integral term in accordance with a value of the deviation.
