The object of the present invention is to provide a fuel cell stack with improved corrosion resistance of metal separators and reduced cost. To attain this object, the fuel cell stack according to the present invention has a cell stack constituted by stacking a prescribed number of unit cells obtained by sandwiching both surfaces of an electrolyte membrane between an anode and a cathode and sandwiching the outer sides thereof with a pair of metal separators, wherein the metal separator positioned on the plus side of the cell stack is subjected to surface treatment providing for relatively higher corrosion resistance than the metal separator positioned on the minus side of the cell stack. Cost reduction can be realized, while maintaining corrosion resistance comparable with that obtained in the case when all the separators are subjected to the anticorrosive surface treatment to the same degree.