Hot stamping method of zinc-plated steel sheet

Upon cooling the galvanized steel sheet (W), below the boiling point of zinc, and the above temperature range ferrite transformation temperature, a change in the emissivity of the surface of the galvanized steel sheet (W), the observation wavelength is not less than 1.4μm measured by the radiation measuring instrument (4), to start the press and quenching in the press hardening apparatus (2), after detecting the end of the alloying reaction based on the change in emissivity. Emissivity measuring device (4) is preferably one measuring element is an InGaAs element or a thermopile.