An X-ray generator including a cathode, an anode provided with two X-ray generation zones, a casing in which the cathode and anode are accommodated, two air cylinders for causing the anode to move, two linear guides for guiding the movement of the anode, and a bellows serving as a seal member. The air cylinders and the linear guides are provided at different positions on a surface orthogonal to a center axis of the bellows. The air cylinders and the linear guides are provided uniformly in relation to the center axis.