A fuel cell power supply device capable of externally supplying electric power in a stable manner is provided. The fuel cell power supply device includes a fuel cell (1), a capacitor (2) connected in parallel to the fuel cell, a voltage boosting means (3) having an input unit connected in parallel to the fuel cell and the capacitor and an output unit connected to a load (M), and for boosting the output voltages of the fuel cell and the capacitor to supply electric power by the boosted voltages to the load, a secondary battery (6) connected to the output unit of the voltage boosting means via a voltage conversion means (7), a first electric power supply unit (10) connected in parallel to the fuel cell and the capacitor and capable of externally supplying electric power, and an electric power supply control means (30) for controlling supply of electric power from the fuel cell, the capacitor, and the secondary battery to the first electric power supply unit, based on the output of the fuel cell and the charge levels of the capacitor and the secondary battery, in a range where the charge level of the capacitor is not lower than its discharge threshold value and the charge level of the secondary battery is not lower than its discharge threshold value.