A controller of a fuel cell system is configured to perform a normal mode in which one of a plurality of injectors is driven in a case where a needed power for the fuel cell stack is lower than a predetermined value, and perform a high load mode in which two or more of the injectors are driven in a case where the needed power is equal to or higher than the predetermined value. The controller is configured to output a driving command to each of the injectors under a condition that the normal mode is to be performed, and detect closing failure in one injector driven under the driving command in a case where a pressure measured by a pressure measurer after a time point at which the driving command is output is lower than a predetermined threshold.