An x-ray tube (1) irradiates an electron beam from a cathode (18) to impact a target (36) and emit x-rays. When the x-ray tube (1) operates, the magnet portion (40) is rotated every fixed time period and positioned at a prescribed rotation position. Due to the rotation of the magnet portion (40), the magnetic field formed by the permanent magnets (42) changes and the irradiation position on the target (36) of the electron beam moves. As a result, the electron beam is irradiated at a new position on the target (36) and the same amount of x-ray as the initial performance is generated.