The present invention relates to a fuel cell device applied in an electronic device. The electronic device has a power supply unit to supply power to it. The fuel cell device comprises a fuel cell, a regulator unit, a microprocessor unit an auxiliary unit and a power loop device. The regulator unit converts the DC voltage of power output by the fuel cell. The microprocessor unit controls the operation of the fuel cell device and carries out computing needed for its operation. The auxiliary unit supports the operation of the fuel cell. The power loop device selects the power output by the fuel cell device to the electronic device, or power input from the electronic device to the fuel cell device.