An improved method for surface treatment of metallic materials is described herein. The improvement exists in that a surface treatment agent and a metallic material to be treated are placed in a treating device, heating of the metallic material to be treated up to a specific upper limit temperature higher than a transformation point of the metallic material and cooling of the metallic material down to a specific lower limit temperature lower than the transformation point are alternately and repeatedly carried out, an appropriate stress is applied to the material when it takes the lower limit temperature, and after an appropriate number of temperature cycles the applied stress is released when the material takes the lower limit temperature.