A fuel cell system including a fuel cell configured to generate power by having an anode gas and a cathode gas respectively supplied to an anode and a cathode of the fuel cell, the fuel cell system comprising: a compressor configured to supply cathode gas to the fuel cell; a driving device configured to drive the compressor; and a control unit configured to control the driving device on the basis of an operating state of the fuel cell, wherein the driving device comprises: at least two driving sources including an electric motor and a turbine to be driven by a working fluid, the working fluid being one selected from the group consisting of the anode gas supplied from a high pressure tank, compressed air, and a refrigerant circulating in a piping for air conditioning; and a clutch in power transmission path for transmitting a drive force of the turbine to the compressor, the clutch being provided between the electric motor and the turbine, and wherein the control unit is configured to: calculate a target output torque of the compressor on the basis of the operating state of the fuel cell; calculate an outputtable torque of the turbine on the basis of a pressure or a flow rate of the working fluid; calculate a differential torque obtained by subtracting the outputtable torque of the turbine from the target output torque of the compressor; drive the compressor by the electric motor and the turbine or drive the compressor only by the turbine with the clutch set in a connected state when the differential torque is smaller than the clutch connection threshold value; and drive the compressor only by the electric motor with the clutch being in a released state when the differential torque is not smaller than the clutch connection threshold value. a compressor configured to supply cathode gas to the fuel cell; a driving device configured to drive the compressor; and a control unit configured to control the driving device on the basis of an operating state of the fuel cell, wherein the driving device comprises: at least two driving sources including an electric motor and a turbine to be driven by a working fluid, the working fluid being one selected from the group consisting of the anode gas supplied from a high pressure tank, compressed air, and a refrigerant circulating in a piping for air conditioning; and a clutch in power transmission path for transmitting a drive force of the turbine to the compressor, the clutch being provided between the electric motor and the turbine, and wherein the control unit is configured to: calculate a target output torque of the compressor on the basis of the operating state of the fuel cell; calculate an outputtable torque of the turbine on the basis of a pressure or a flow rate of the working fluid; calculate a differential torque obtained by subtracting the outputtable torque of the turbine from the target output torque of the compressor; drive the compressor by the electric motor and the turbine or drive the compressor only by the turbine with the clutch set in a connected state when the differential torque is smaller than the clutch connection threshold value; and drive the compressor only by the electric motor with the clutch being in a released state when the differential torque is not smaller than the clutch connection threshold value. at least two driving sources including an electric motor and a turbine to be driven by a working fluid, the working fluid being one selected from the group consisting of the anode gas supplied from a high pressure tank, compressed air, and a refrigerant circulating in a piping for air conditioning; and a clutch in power transmission path for transmitting a drive force of the turbine to the compressor, the clutch being provided between the electric motor and the turbine, and wherein the control unit is configured to: calculate a target output torque of the compressor on the basis of the operating state of the fuel cell; calculate an outputtable torque of the turbine on the basis of a pressure or a flow rate of the working fluid; calculate a differential torque obtained by subtracting the outputtable torque of the turbine from the target output torque of the compressor; drive the compressor by the electric motor and the turbine or drive the compressor only by the turbine with the clutch set in a connected state when the differential torque is smaller than the clutch connection threshold value; and drive the compressor only by the electric motor with the clutch being in a released state when the differential torque is not smaller than the clutch connection threshold value. calculate a target output torque of the compressor on the basis of the operating state of the fuel cell; calculate an outputtable torque of the turbine on the basis of a pressure or a flow rate of the working fluid; calculate a differential torque obtained by subtracting the outputtable torque of the turbine from the target output torque of the compressor; drive the compressor by the electric motor and the turbine or drive the compressor only by the turbine with the clutch set in a connected state when the differential torque is smaller than the clutch connection threshold value; and drive the compressor only by the electric motor with the clutch being in a released state when the differential torque is not smaller than the clutch connection threshold value.