A fuel cell system installed in a fuel-cell movable body. The system includes a fuel cell for generating electric power using reaction gases; a plurality of sensors for measuring states of the fuel cell; an abnormal state detecting device for detecting an abnormal state of at least one of said plurality of sensors; a substitution possibility determining device for determining whether there are one or more substitution sensors from among said plurality of sensors, each substitution sensor outputting a signal value used for setting a substitutional value for a signal value output from the sensor whose abnormal state has been detected; and a predetermined operation control device for operating the fuel cell in a predetermined operation state when the abnormal state of the sensor is detected by the abnormal state detecting device and it is determined by the substitution possibility determining device that there is no substitution sensor.