PURPOSE: To increase the capacity of a X-ray tube, by means of cooling from a brush tangent to a rotary anticathode.

CONSTITUTION: Generated X-ray is utilized by means of causing an anticathode 3 to be struck by accelerating electron 2 from an electron gun 1. The anticathode 3 of this X-ray tube is caused to be rotated at a high speed, and is subjected not to be dissolved by the collision of electron, and is cooled forcibly with water etc. by means of making the inner part into an empty. A further forced cooling is performed by the fluid of natural cooling or inlet/outlet tubes 7, 8 by means of causing a brush to be contacted to the heated part near to the focus of electron of a focus surface 4, or to the position not to be obstructed from the injection of the X-ray by setting up a brush 6. It can increase the effect by means of cooling by Peltier effect or Thomson effect, by flowing direct current between the anticathode and the brush 6. By such means, the capacity of X-ray tube can be increased by adding the cooling by the brush.