An x-ray device has a cathode aligned on a target region in a tube housing with a rotating anode unit. The rotating anode unit is borne to rotate around a rotational axis inside the tube housing. The rotating anode unit has a rotating anode plate with the target region and a shaft rotationally connected with the rotating anode plate. A magnetic bearing supports the shaft without contact in the tube housing. The rotating anode plate has an axial extension facing away from the shaft. The axial extension dips into a fluid-filled receptacle space of the tube housing for heat dissipation. Such an x-ray device allows high rotation speeds of the rotating anode unit, and thus a high operational power.