PURPOSE: To equalize the brightness and contrast in the entire surface of a screen even at a low magnification, by providing the frame of an X-ray spectroscope which can be moved freely, and adjusting the position corresponding to an incident slit at the surface of a specimen.

CONSTITUTION: The specimen S is irradiated by an electron beam 3, and the wavelength of the X-ray generated from the specimen S is dispersed by a spectroscopic crystal C and sensed by an X-ray sensor D. The frame 5 of the X-ray spectroscope, wherein said crystal C, sensor D, and the like are provided, is freely moved by a screw F which is externally operated via a universal shaft 7, with a shaft 6 as a center. The movement of the frame 5 is controlled for every scan corresponding to the deflection of the electron beam through a converging lens 1 caused by a counter, a step motor, and the lkie. Then, the position of the incident slit is adjusted to a center O and both ends O' and O" on the surface of the specimen 3. when the result of three scans are overlapped, the brightness and contrast in the entire surface of screen are equalized even at the low magnification by uniformly distributed irradiation.