PURPOSE: To obtain a narrow spectral band pyrometer for measuring the temperature of an object like a semiconductor wafer coated with a film having an absorption band.

CONSTITUTION: The pyrometer collects the thermal radiation radiated from an object 1 to a radiation detector 6 via a lens 3, an aperture 4 and a filter 5, and measures the strength of the radiation. The filter 5 has a pass band included in the range of the absorption band of the film 2. The detected radiation has the wavelength of the heated object being substantially opaque, and the influence of the inaccuracy of emissivity in the temperature measurement is minimized. The filter 2 has the absorption band included in the pass band of the filter 5, and has the sufficient thickness that, when the object 1 is observed via the filter 5, it is observed opaque. Or, the film 2 is the material with the thickness known that the emissivity is constant and accurate in the wavelength range of the pass band.