Provided are a fuel cell system and a control method thereof capable of inhibiting the occurrence of problems caused by surplus electrical power even in cases where the torque able to be generated by the motor is limited due to a low motor drive voltage. A fuel cell system provided with a fuel cell and a motor is further provided with required output torque calculation means for calculating a required output torque based on an output requirement, torque upper limit value calculation means for calculating a torque upper limit value of torque able to be generated by the motor based on a drive voltage of the motor, required motor torque calculation means for calculating a required motor torque based on the required output torque and the torque upper limit value, required motor power calculation means for calculating a required motor power based on the required motor torque, and required generated power calculation means for calculating a required generated power of the fuel cell based on the required motor power.