Abstract: An air-cooled fuel cell system comprises a cell stack including substacks and cooling plates arranged between neighbouring two substacks, each substack comprising a plurality of unit cells, and bipolar plates each having fuel channels and process air channels and being arranged between two unit cells, said unit cells and bipolar plates being arranged in a stack and electrically connected in series. The fuel cell system further comprises a process air inlet manifold mounted on one peripheral face of the cell stack where inlets of said process air channels are opened, a cooling air manifold mounted on said process air inlet manifold, said cooling plates extending from the peripheral face of the cell stack and passing through the process air manifold in such a manner that the cooling air passages provided therein are communicated with said cooling air manifold.