To provide a high corrosion resistance impartment surface treatment method using an alkali aqueous solution for reinforcing a passive film of stainless steel without using a strong acid or a strong oxidizing agent.

In the surface treatment method for stainless steel, stainless steel is dipped into a nonoxidizing alkali aqueous solution for ≥24 hr. As the nonoxidizing alkali aqueous solution, the one comprising 40 to 60 mass% NaOH and heated at 70 to 100°C is preferable. An extremely thick film compared with a passive film by the conventional technique can be formed by dipping the stainless steel into the nonoxidizing aqueous solution. Further, the film obtained by the method becomes the dense amorphous film and exhibits high corrosion resistance since the concentration of Cr is made higher than the concentration of Fe.