A method of producing a fuel cell comprising the steps of: (A) molding a separator having a gas flow channel or a cooling water flow channel by injection molding process having a step of injecting a mixture comprising one or more conductive inorganic materials and one or more resins into a mold; (B) producing an assembly comprising an electrolyte and a pair of electrodes sandwiching the electrolyte; and (C) combining the separator with the assembly to produce a fuel cell.