To provide an infrared high-temperature observation furnace having the thickness of the whole body of the observation furnace thinner than that of the conventional one and having superior handling performance.

This observation furnace is provided with decompressible unit hermetical chambers 7a and 7b comprising an assembly of elliptical cross-section parts OP. This observation furnace is also provided with an installation part 9 of a test material 100 positioned in one focus F1 of the ellipses, heating parts 21 of heater lamps 20 positioned in the other focuses F2 and F2 of the ellipses, and an observation window 40 positioned adjacent to the installation part 6 for observing the test material 100. The unit hermetical chambers 7a and 7b are rotary bodies of the elliptical cross-section parts OP and the observation-direction axis S1 of the observation window 40 approximately orthogonally crosses with the long axis S2 of the ellipses.