A fuel cell device comprises a fuel cell stack which is formed from a plurality of unit cells stacked one above the other in a stacking direction, each unit cell having one or more media channels and a membrane electrode assembly that comprises a cathode, an anode, and a membrane arranged between the cathode and the anode, and comprising a media duct running substantially parallel to the stacking direction. The media duct is connected or can be connected to the fuel cell stack to conduct a medium into or out of the media channels of the unit cells of the fuel cell stack substantially laterally to the stacking direction. The media duct is formed as a functional component or such a functional component is integrated therein, which is formed to pre-treat the medium before it enters the media channels or to post-treat the medium after it has exited the media channels.