A fuel cell system includes, an oxidant feeder configured to supply an oxidant to a fuel cell, an oxidant passage which communicates with the fuel cell, a bypass passage which branches from the oxidant passage and along which part of the oxidant flows so as to bypass the fuel cell, a bypass valve which is provided in the bypass passage, an oxidant quantity-of-flow control unit which is configured to supply the quantity of flow of the oxidant corresponding to an amount of electricity required by the fuel cell, and an oxidant quantity-of-flow control unit for a sound vibration mode configured to supply a constant quantity of flow of the oxidant, and further includes a bypass valve control unit configured to control the bypass valve according to a requirement of the fuel cell when the oxidant quantity-of-flow control unit for the sound vibration mode controls the oxidant feeder.