A fuel cell system comprising: a fuel cell including an anode and a cathode; a cathode gas passage supplying a cathode gas to the cathode of the fuel cell; a reformer reforming a source gas to generate an anode gas; a source gas passage including a gas supply source that supplies the source gas in a desulfurized state to the reformer; and an anode gas passage supplying the anode gas generated at the reformer to the anode of the fuel cell, wherein the source gas passage includes a first desulfurizer where the source gas is desulfurized without an addition of hydrogen, the first desulfurizer being arranged in a first environment and including a desulfurization performance relative to a source gas having a dew point equal to or larger than a given value, and the source gas passage includes a second desulfurizer arranged in a second environment having a lower temperature than the first environment, the second desulfurizer including a desulfurization performance relative to a source gas having a dew point lower than the given value and the source gas having the dew point equal to or larger than the given value, characterized in that the desulfurization performance of the second desulfurizer relative to the source gas having the dew point equal to or larger than the given value is lower than the desulfurization performance of the second desulfurizer relative to the source gas having the dew point lower than the given value, the source gas passage includes a flowmeter measuring a flow volume of the source gas, and the first desulfurizer, the second desulfurizer, and the flowmeter are arranged at the source gas passage in a state where an arrangement order is the first desulfurizer, the second desulfurizer, and the flowmeter from an upstream side to a downstream side of the source gas passage in a flow direction of the source gas. a fuel cell including an anode and a cathode; a cathode gas passage supplying a cathode gas to the cathode of the fuel cell; a reformer reforming a source gas to generate an anode gas; a source gas passage including a gas supply source that supplies the source gas in a desulfurized state to the reformer; and an anode gas passage supplying the anode gas generated at the reformer to the anode of the fuel cell, wherein the source gas passage includes a first desulfurizer where the source gas is desulfurized without an addition of hydrogen, the first desulfurizer being arranged in a first environment and including a desulfurization performance relative to a source gas having a dew point equal to or larger than a given value, and the source gas passage includes a second desulfurizer arranged in a second environment having a lower temperature than the first environment, the second desulfurizer including a desulfurization performance relative to a source gas having a dew point lower than the given value and the source gas having the dew point equal to or larger than the given value, characterized in that the desulfurization performance of the second desulfurizer relative to the source gas having the dew point equal to or larger than the given value is lower than the desulfurization performance of the second desulfurizer relative to the source gas having the dew point lower than the given value, the source gas passage includes a flowmeter measuring a flow volume of the source gas, and the first desulfurizer, the second desulfurizer, and the flowmeter are arranged at the source gas passage in a state where an arrangement order is the first desulfurizer, the second desulfurizer, and the flowmeter from an upstream side to a downstream side of the source gas passage in a flow direction of the source gas.