Abstract: The present invention relates to a high-temperature microscope. According to this invention, a specimen is held in vacuum with one side of it heated through exposure to an electron beam and the other side of it observed through an observation window.A curtain of inert gas is formed between the specimen and the observation window to prevent the window from being clouded, i.e., to prevent vapor deposit on the window from the specimen.Visual observation (including photography) and measurement of the specimen temperature by heat radiation therefrom are done individually with different bands of wavelengths. For the purpose of illuminating the specimen, beams of spectral distribution containing the components of in the visible band for observation are used but no components of the temperature-measuring band are utilized as light source. For the purpose of visual observation, a narrow visible band contained in the aforesaid beam located in low brightness in the heat radiation beams from the specimen is utilized.