PURPOSE: To improve the accuracy of measurements by setting a total reflection angle within a local extent on the surface of a semiconductor substrate and accurately setting the angle of total reflection fluorescent X-ray analysis.

CONSTITUTION: A stage 16 can be moved in the vertical direction by means of a stepping motor incorporated in a supporting base 15, and a semiconductor substrate 14 set on the stage 16 can be set at an arbitrary angle against an X-ray beam 12 which is emitted toward a scintillation counter 13 from an X-ray source 11. Simultaneously with the X-ray beam 12, microwaves are radiated to the substrate 14 from a microwave generator 17. The microwaves radiated to the substrate 14 are reflected by electrons excited on the surface of the substrate 12 and the reflected microwaves are detected by means of a microwave detector 18. The critical total reflection angle of the microwaves is obtained from the intensity fluctuation of the reflection of the microwaves and used as a reference position and the stage 16 is inclined in the direction in which the angle of the substrate 14 becomes smaller.