[Problem] Even when the ambient temperature rises and the pressure in the fuel gas system rises while the operation of the fuel cell stack or the fuel cell module is stopped, the possibility that the pressure in the fuel gas system exceeds the design pressure of the fuel gas system is reduced.
[Solution] A fuel cell system includes: a fuel cell module having a fuel cell stack; a fuel gas system that supplies a fuel gas to the fuel cell stack; an upstream-side block valve and a downstream-side block valve that open and close the fuel gas system; a vent system that is provided to branch from the fuel gas system between the upstream-side block valve and the downstream-side block valve; and a bleed valve that opens and closes the vent system. When an operation of the fuel cell stack is to be stopped, pressure reduction control, in which the bleed valve is opened after the upstream-side block valve is closed, and then the downstream-side block valve is closed after a predetermined time has elapsed, is performed.