A fuel cell system capable of reliably and rapidly discharging liquid in a fuel cell stack to the outside is provided. In a fuel cell system having a discharge path (76) that allows discharge of at least liquid in a fuel cell stack (20), at the time of actuation of the fuel cell stack (20), reaction gas is supplied to the fuel cell stack (20) at a higher speed or in a greater amount than during normal operation of the fuel cell stack (20). By supplying the reaction gas at a high speed or in a great amount before actuation, residual liquid in the fuel cell stack (20) can be blown off and thus reliably and rapidly discharged to the outside. The residual liquid can be discharged more easily when a volume (30) is provided in the discharge path (76) or the pressure inside the fuel cell stack (20) is set to a negative level at the time of actuation thereof.