PURPOSE: To obtain a highly accurate, simple emissivity meter, which can use a highly reliable, low temperature black body furnace, by attaching a cylinder, which comprises a high heat conduction material and whose inside is painted by a high-emissivity paint, to the peripheral part of a sensor.

CONSTITUTION: A heat transfer body 1 forming the main body of a sensor is manufactured by a highly heat-conductive metal material such as aluminum so that the temperature of the surface 2 of the heat transfer body, on which black color is applied, becomes uniform. On the inner surface of a cylinder 7, a black paint having high emissivity is applied in order to increase the emissivity. Heat rays are inputted to a sample to be measured approximately uniformly from an upper half sphere. The thermal quantity, which is lost from a detecting part 5 of the sensor 4 by the heat conduction of air, can be largely reduced. As a result, even though the sensor 4 is placed on a black body furnace or on a plate, which is painted in black color, the temperature of the detecting part is hardly changed. Therefore, as the standard of the emissivity 1, a low temperature black body furnace, whose diameter is the same as that of the sensor 4, can be utilized. The accuracy of the measured emissivity can be improved.