GROUND FAULT DETERMINATION SYSTEM AND GROUND FAULT DETERMINATION METHOD

A ground fault determination system includes an acquisition unit that acquires the degree of deterioration of a plurality of fuel cell stacks connected in parallel with each other and connected to an inverter, a ground fault detection unit that detects insulation resistance between the inverter and the plurality of fuel cell stacks, a first determination unit that determines, when the deterioration of each fuel cell stack has not yet progressed, whether there is a ground fault with all the fuel cell stacks all at once, and a second determination unit that determines in turn, when the deterioration of at least one fuel cell stack has progressed, whether there is a ground fault with each fuel cell stack.