In a fuel cell system, an electrically conductive first case unit and an electrically conductive second case unit are fixed by screws such that insulating members are interposed between the first case unit and the second case unit. A load applying mechanism is provided in the first case unit. A fuel cell stack, a heat exchanger, and a reformer are provided in the second case unit. One pole of the fuel cell stack is electrically connected to the first case unit through an electrically conductive end plate, and the other pole of the fuel cell stack is electrically connected to the second case unit through an electrically conductive end plate.