To allow an angle between an X-ray main radiation direction of an X-ray tube and a target inclined surface to be varied.

A flexible tubular part 50 formed into a bellows shape is arranged between a large-diameter part 40 of an envelope 16 of this X-ray tube 10 and a positive electrode insulation part 44. By applying a tensile force to an positive electrode end 30 of a positive electrode 12, the flexible tubular part 50 of the envelope 16 is bent (the right side 50a is extended and the left side 50b is contracted), the center axis 27 of the positive electrode 12 is inclined with respect to the X-ray main radiation direction 51, and a target angle 52 formed by the X-ray main radiation direction 51 and the inclined surface 28 of a target 18 is increased, whereby an X-ray radiation range is resultantly increased. By changing the tensile force applied to the positive electrode end 30 of the positive electrode 12, the increase of the target angle 52 and that of the X-ray radiation range can be changed.