The present invention provides a fuel cell system, a control unit controls the operations of the auxiliary units, that are air pump (22), the fuel pump (23), and the cooling fan (25), based on the volume of an electronic musical instrument (50). When the electronic musical instrument (50) performs large volume, and consumes large electric power, the motor driving the auxiliary units increases rotation speed and generates large volume. The performance of music may not be interfered even the driving volume generated by the auxiliary units increases when the performance volume increase. In addition, when the electronic musical instrument (50) performs small volume, and consumes small electric power, the auxiliary units operation is limited, and driving sound generated by the auxiliary units also reduces. The power generating volume and sound generated by the auxiliary units change according to power desired by the electronic musical instrument (50), that is volume of music performed by the same. The fuel cell system reduces the noise of the auxiliary causing interfere to the electronic musical instrument performance in condition of not changing fuel cell design.