The present invention provides a fuel cell system capable of accurately controlling the pressure of fuel gas supplied to the fuel cell, the fuel cell system comprising: a fuel gas supply line (SL) which supplies the fuel gas from a fuel gas supply source (11) to the fuel cell (10); pressure-regulating means (RG) provided on the fuel gas supply line (SL) and for regulating the pressure of the fuel gas supplied from the fuel gas supply source (11); and a circulation route (R) which returns the fuel gas discharged from the fuel cell (10) to the fuel gas supply line (SL), wherein the circulation route (R) is connected to the fuel gas supply line (SL) such that the fuel gas is returned thereto in the upstream of the pressure-regulating means (RG).