A fuel cell system provided with a fuel cell module, a water supply device for supplying water to the fuel cell module, a water container for supplying water to the water supply device, and a condenser for condensing water vapor in the exhaust gas which is discharged from the fuel cell module and supplying the condensed water to the water container. The water container contains therein an ion exchange device for removing impurities which are contained in the water supplied from the condenser. The water supply device is provided below and downstream of the water container. A pressure regulating device for absorbing a pulsation of the water supply device and absorbing the variation in the pressure in the fuel cell module is provided between the water supply device and the fuel cell module.