Provided is a stainless steel for fuel-cell separators, said steel having a low surface contact resistance. Said stainless steel contains at least 16-40% chromium by mass, and regions having microscopic concavities and convexities, namely those wherein the mean distance between concavities or convexities is 20 to 150 nm as observed by a scanning electron microscope, cover at least 50% (preferably at least 80%) of the surface of the stainless steel.