A stainless steel sheet useful as a separator for a low-temperature fuel cell has the surface state that a lot of fine projections (p) stand close together around many fine pits (d) formed over a whole surface. The surface state is realized by alternating electrolytic etching in a ferric chloride solution. When the stainless steel separator is built in a fuel cell, contact resistance between the separator and a graphite electrode is kept at a lower level even in a corrosive atmosphere. Consequently, the fuel cell can be driven with high power-generating efficiency over a long term even under severely corrosive conditions without generation of massive Joule heat.