PURPOSE: To permit X-ray analysis even if the incident quantity of X-rays entering an energy dispersion type X-ray spectroscope (EDS) at the max. stroke is large by providing an X-ray incidence limiting stop in front of said spectroscope and operating the spectroscope from the atm. side.

CONSTITUTION: Electron rays 3 are projected to a sample 3 disposed in a body 1 of an electron microscope or the like to generate X-rays. A wavelength dispersion type X-ray analyzer (WDS) and EDS 8 are provided in the body 1 in order to spectrally split the X-rays. A semiconductor X-ray detector of the EDS 8 is mounted to the front end of a heat conductive bar 12 protected in a protective pipe 14 and is charged into the body 1. The pipe 14 is moved by the operation of an operation handle 10 from the atm. side by a moving stage 7 while the vacuum in the body 1 is maintained. An incident X-ray variable stop mechanism 15 is mounted to the front face of the X-ray detector 13 so as to move integrally with the pipe 14. The incident X-ray quantity by the mechanism 15 is changed over by a knob 16 mounted to the atm. side thereof while the vacuum in the body 1 is maintained.