A fuel cell vehicle drives a motor (9) with electric power from a fuel cell power system (100) comprising a fuel cell (4) which generates electricity using hydrogen and oxygen. A controller (10) calculates an electrical load demand required to run the vehicle. When this value is below a predetermined load, it performs constant load operation of the fuel cell power system (100), and when the predetermined load value is exceeded, it operates it under a load according to the electrical load demand. The demand for resolution and precision of the various sensors or flowrate control valves installed in the fuel cell power system and thereby suppressed, costs can be reduced, and fuel cost-performance is improved by continuing an efficient operating state.