A fuel cell system includes a plurality of electricity generation systems and a connection flow path through which fuel flows between the plurality of electricity generation systems. Each electricity generation system includes a fuel tank, a fuel cell stack, a fuel flow path, a first pressure sensor, a shutoff valve, a control device, and a branch portion. The first pressure sensor is arranged in the fuel flow path and detects a fuel pressure on the fuel tank side. The shutoff valve is arranged on a downstream side of the first pressure sensor in the fuel flow path, and is switched between flow and shutoff of the fuel by opening and closing. The branch portion branches from the fuel flow path on a downstream side of the shutoff valve in the fuel flow path. The connection flow path connects the mutual branch portions of the plurality of electricity generation systems.