A power conditioning system that includes a fuel cell to be connected to a load, a fuel cell converter connected between the fuel cell and the load, the fuel cell converter converting an output voltage of the fuel cell at a predetermined required voltage ratio, a battery connected in parallel with the fuel cell with respect to the load, the battery serving as a power supply source different from the fuel cell, a battery converter connected between the battery and the load, the battery converter converting an output voltage of the battery at a predetermined required voltage ratio. The power conditioning system includes a converter direct coupling unit configured to directly couple an input side and an output side of the fuel cell converter during startup of the power conditioning system and a fuel cell output voltage increasing unit configured to increase the output voltage of the fuel cell to a predetermined voltage by supplying oxidant gas during startup of the fuel cell.