PURPOSE: To freely adjust the energy width of X-rays by arranging an X-ray source, a spectral crystal and a sample on the circumference of a Rowland circle and making the diameter of the X-ray source and the use region of the spectral crystal variable by adjusting the slit between the X-ray source and the sample.

CONSTITUTION: An X-ray source, a spectral crystal 2 and a sample 3 are arranged on the circumference of a Rowland circle and a target 1b is irradiated with electron beam from an electron gun to generate characteristic X-rays from the region (d) of the target 1b. The X-rays are limited by a slit 10 and the crystal 2 is irradiated with the X-rays from the minute region (l) of the slit 10. Herein, by adjusting the width and position of the slit by a slit adjusting means 11 and a slit moving means 12, the size of the X-ray source and the use region of the crystal 2 can be made variable and the energy width of X-rays can be freely adjusted. Further, in arbitrarily set energy width, the max. intensity of X-rays can be obtained.