PURPOSE: To provide a thin film X-ray diffraction equipment in which the diffracted X-ray can be measured with sufficient intensity even if the X-ray is incident at a shallow angle.

CONSTITUTION: In an X-ray diffraction equipment where X-rays are incident on the surface of a sample at a predetermined angle, the secondary X-rays emitted therefrom are detected by a detector, and the structure or composition of the sample is studied for the purpose of identification, an optical system 4 comprising a bundle of a plurality of X-ray tubes for detecting only the parallel secondary X-rays having specific angle selectively from the secondary X-rays 3 emitted from a thin film sample 2 or a predetermined area on the surface thereof is disposed between the sample 2 and the detector 5.