The present invention relates to an X-ray generating apparatus. A moving part(3) for holding an X-ray irradiation window (5) of a target (4) is connected to the body portion (1) of a vacuum container via the vacuum bellows (2), and a guiding mechanism for limiting the moving direction and the inclination of the moving part (3) is arranged outside the vacuum container. The guiding mechanism includes a guide flat surface (10a) formed on a side of the main body (1) along a plane orthogonal to the central axis of the electron beam (B), a flat surface (13a) for guiding the movable flat surface 13a, (3) is formed so as to face the guide flat surface (10a); and a plurality of rotating bodies (12) which are rotatable therebetween. As a result, the frictional force in the guiding mechanism can be reduced.