An X-ray diffraction apparatus includes: an X-ray source (110); a first incident path letting the generated X-ray beam pass therethrough; a second incident path letting the generated X-ray beam be reflected by a multilayer film mirror and letting the reflected X-ray beam pass therethrough in parallel with the X-ray beam having passed through the first incident path. A movement mechanism is provided moving the X-ray source (110) between the first incident path and the second incident path while preserving respective relative positions thereof. An incident slit (160) allows an X-ray beam to be incident on a sample S pass therethrough; and a sample support stage (165) supports the sample S at a position fixed relative to the incident slit (160).