A fuel cell system comprises: a fuel container for storing fuel liquefied with pressure; a reformer for generating hydrogen from the fuel through a catalyst reaction based on heat energy; an electric generator for generating electricity by transforming energy of an electrochemical reaction between hydrogen and oxygen into electric energy; a condenser for condensing water produced in the electric generator; and a heat exchanger passing through the condenser for cooling the condenser by latent heat of the fuel. With this configuration, cooling water cooled by latent heat of a fuel container is employed to cool the condenser without using a separate cooler. Furthermore, air is mixed with butane fuel without using a separate power unit, so that it is possible to achieve a more compact and highly efficient fuel cell.