To provide a temperature measuring device which perform temperature measurement and its correction with high precision by attaching a continuous- measuring radiation thermometer and a correcting contact thermometer to the same flange with the first and second cooling hoods in between.

When surface temperature of a steel plate 13 is measured online with a radiation thermometer 18 under the condition where the first and second cooling hoods 15 and 16 and a radiation shield 17 are cooled. At this time, though the temperature of the steel plate 13, at a measurement position, is going to rise due to radiated heat front a furnace wall 12a, the action of the radiation shield 17 prevents the rising of temperature. And when the radiation thermometer 18 is corrected, a rod 20a of an air cylinder 20 is advanced/receded, and, in the second cooling hood 16 under the cooling condition, after a sensor head 19a is lowered and brought into contact with the surface of the steel plate 13, the temperature of steel plate 13 is measured. And, by assigning the radiation thermometer 18 and the contact thermometer 19 near each other, temperature change of the steel plate before measurement with each thermometer is suppressed to a minimum.