Abstract: On part of a surface of a metal sheet that is to be heated by radiant heat transfer with a near-infrared ray, a region where reflectance for a radiant ray is made lower than that of the original surface of the metal sheet is formed. As reflectance reducing treatment, painting or thermal spraying in a blackish color, plating in a blackish color, treatment for increasing roughness of the surface of the metal sheet, blasting, etching, blackening, surface layer quality changing treatment of the metal sheet, or the like can be adopted. The metal sheet is turned into a heated metal sheet partially having a different temperature by being heated by radiant heat transfer, and thereafter, the heated metal sheet is subjected to thermal processing accompanied by cooling, for example, by hot stamping.

Abstract: On part of a surface of a metal plate that is to be heated by radiant heat transfer with a near-infrared ray, a region where reflectance for a radiant ray is made lower than that of the original surface of the metal plate is formed. As reflectance reducing treatment, painting or thermal spraying in a blackish color, plating in a blackish color, treatment for increasing roughness of the surface of the metal plate, blasting, etching, blackening, surface layer quality changing treatment of the metal plate, or the like can be adopted. The metal plate is turned into a heated metal plate partially having a different temperature by being heated by radiant heat transfer, and thereafter, the heated metal plate is subjected to thermal processing accompanied by cooling, for example, by hot stamping.