PURPOSE: To obtain an X-ray television system capable of obtaining a high quality image capable of high resolution characteristic.

CONSTITUTION: In order to slightly change the diameter of the output image of an X-ray image tube, the resistance value of a breeder resistance R1 is made variable. By changing voltage to be applied to an auxiliary electrode 6, a focal distance is changed and the diameter of the output image of an output surface 4 is changed. By changing the focal distance of a zoom lens 7, the size of the output image to be formed and projected on the picture element of the input surface of a CCD camera 8 is adjusted, as to the output image formed on the output surface 4 of the X-ray image tube 1. In the case of shortage of field of view where the diameter of the output image of the X-ray image tube 1 is large, the size of the output image to be formed is reduced. In the case of thortage of picture element where the diameter of the output image is small, the size of he output image to be formed is increased. The size of the output image is adjusted to an image pickup area A.