To provide a method or the like capable of measuring accurately even a surface temperature of a steel product in a low temperature zone of about 400°C.

This surface temperature measuring device 100 equipped with a radiation thermometer 1 arranged oppositely to a steel product M whose temperature is to be measured measures the surface temperature of the steel product whose temperature is to be measured by detecting thermal radiation light radiated from the surface of the steel product whose temperature is to be measured by the radiation thermometer. The surface temperature measuring device is also equipped with an optical filter for blocking light having the wavelength below 1.00 μm and light having the wavelength longer than 1.20 μm between the steel product whose temperature is to be measured and a detection element of the radiation thermometer, and preferably is equipped with a nozzle 2 for spraying purge water between the surface of the steel product whose temperature is to be measured and the radiation thermometer.

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