NOVELTY - Fuel cell system comprises: (a) an anode gas circulation path comprising an anode gas supplying path and an anode gas ejection path, an anode gas flowing through the anode gas supplying path and the anode gas ejection path; (b) a fuel cell generating electricity by receiving a supply of the anode gas through the anode gas supplying path; (c) a blowdown valve provided in the anode gas ejection path; and (d) a control unit controlling the blowdown valve.    USE - Used as a fuel cell system.    ADVANTAGE - The fuel cell system can prevent the anode gas flow path from freezing, and can perform a scavenging process with reliability.    DETAILED DESCRIPTION - Fuel cell system comprises: (a) an anode gas circulation path comprising an anode gas supplying path and an anode gas ejection path, an anode gas flowing through the anode gas supplying path and the anode gas ejection path; (b) a fuel cell generating electricity by receiving a supply of the anode gas through the anode gas supplying path; (c) a blowdown valve provided in the anode gas ejection path; and (d) a control unit controlling the blowdown valve. The control unit comprises a freeze estimation unit estimating whether the anode gas circulation path is likely to freeze, a pressure reduction unit reducing a pressure of the anode gas circulation path, and a pressure condition confirmation unit confirming a pressure of the anode gas circulation path. When the freeze estimation unit estimates a freezing when the fuel cell stops generating electricity, the blowdown valve is closed, a pressure of the anode gas circulation path is reduced by the pressure reduction unit, and, the blowdown valve is opened after the pressure condition confirmation unit confirms that a pressure of the anode gas circulation path reaches a predetermined pressure less than or equal to an atmospheric pressure, thus moving a moisture inside the anode gas circulation path in a direction towards the fuel cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a diagram of the fuel cell system.    Fuel cell (11)    Anode gas ejection path (35)    Control unit (45)    Anode gas circulation path (46)    Power consumption device (50)    Blowdown valve (52)