Fabricating method of stainless steel used for fuel cell separator, stainless steel used for fuel cell separator, fuel cell separator and fuel cell

To provide a method for producing stainless steel having excellent conductivity and durability for use in a fuel cell separator, stainless steel for use in a fuel cell separator, a fuel cell separator, and a fuel cell. Specifically, the stainless steel for use in a fuel cell separator is produced by subjecting stainless steel containing 16 mass% or more of Cr to electrolytic treatment and thereafter to immersion treatment in a solution containing fluorine. The electrolytic treatment is carried out by anodic electrolyzation or by a combination of anodic electrolyzation and cathodic electrolyzation, and an anodic electrolytic quantity Qa and a cathodic electrolytic quantity Qc preferably satisfy the relationship: Qa ‰¥ Qc. The solution containing fluorine preferably has a temperature of 40°C or higher, and hydrofluoric acid concentration [HF] (mass%) and nitric acid concentration [HNO 3 ] (mass%) satisfying the relationship: [HF] ‰¥ 0.8 × [HNO 3 ].