An anode target is roratably supported by a rotating mechanism having a rotary body and a staionary body. A fitted portion between the rotary body and the stationary body is formed of bearing areas having dynamic pressure type sliding bearings and a non-bearing area having a clearance between the rotary body and the stationary body larger than that in the bearing areas. The rotary body facing the non-bearing area is positioned where a time for heat transfer from the anode target is shorter than the rotary body facing the bearing areas. Thus, the characteristics of heat radiation from the anode target can be improved, and a stable bearing operation can be maintained.