A fuel cell system is provided with: a fuel supplier supplying a fuel including dimethyl ether; a reforming catalyst causing a reforming reaction of the fuel into a reformed gas including hydrogen; a shift catalyst causing a shift reaction of the reformed gas; a methanation catalyst causing a methanation catalyst of the reformed gas; a hydrogenation catalyst causing a hydrogenation catalyst of the reformed gas; and a fuel cell using hydrogen formed the reforming reaction and the shift reaction from the fuel and oxygen included in an atmospheric air to generate electricity.