A fuel cell system comprising a fuel cell and a secondary cell as power supply sources to a load (13, 14, 25, 26), the system comprising: a fuel cell power supply path that connects the fuel cell and a first load (13, 14); a first converter provided on the fuel cell power supply path, the first converter being capable of boosting an output of the fuel cell; a first secondary cell power supply path that connects the secondary cell to a first connecting point on the fuel cell power supply path located closer to the first load side than the first converter; a second converter provided on the first secondary cell power supply path, the second converter being capable of boosting an output of the secondary cell; a second secondary cell power supply path that connects a second load (25, 26) to a second connecting point on the first secondary cell power supply path located between the second converter and the secondary cell; a first control part that controls the first converter; and a second control part that controls the second converter, wherein, during normal operation, the first control part allows the first converter to control an output voltage of the fuel cell, and the second control part allows the second converter to control an output voltage to the first load side, and wherein, during occurrence of an abnormality such as a failure of the secondary cell, the first control part allows the first converter to control an output voltage thereof, and the second control part allows the second converter to control an output voltage to the second load side; characterized in that, during occurrence of the abnormality of the secondary cell, the output voltage of the first converter is controlled at a constant voltage and the output voltage of the second converter to the second load side is controlled so as to match a requested output of the second load (25, 26). a fuel cell power supply path that connects the fuel cell and a first load (13, 14); a first converter provided on the fuel cell power supply path, the first converter being capable of boosting an output of the fuel cell; a first secondary cell power supply path that connects the secondary cell to a first connecting point on the fuel cell power supply path located closer to the first load side than the first converter; a second converter provided on the first secondary cell power supply path, the second converter being capable of boosting an output of the secondary cell; a second secondary cell power supply path that connects a second load (25, 26) to a second connecting point on the first secondary cell power supply path located between the second converter and the secondary cell; a first control part that controls the first converter; and a second control part that controls the second converter, wherein, during normal operation, the first control part allows the first converter to control an output voltage of the fuel cell, and the second control part allows the second converter to control an output voltage to the first load side, and wherein, during occurrence of an abnormality such as a failure of the secondary cell, the first control part allows the first converter to control an output voltage thereof, and the second control part allows the second converter to control an output voltage to the second load side; characterized in that, during occurrence of the abnormality of the secondary cell, the output voltage of the first converter is controlled at a constant voltage and the output voltage of the second converter to the second load side is controlled so as to match a requested output of the second load (25, 26).