PURPOSE: To reduce the amt. of X-ray exposure to an examinee and to shorten the time needed for setting when a field of X-ray radiation is set during a picture under compression is taken.

CONSTITUTION: The first and the second switching circuits SW1 and SW2 which switch a set electric voltage for setting a field of X-ray radiation in accordance with an operational signal of a compression cylinder output from an operational table 30 and a loaded electric voltage for setting an electron enlarging ratio of an image intensifier, are provided. At the same time when the compression cylinder used for taking a picture of a compression image is inserted into a picturing space, the field of X-ray radiation and the electron enlarging ratio are automatically set, the conventional working process wherein the field of X-ray radiation is set while the fluoroscopic image of the examinee is observed is eliminated to reduce the amt. of X-ray exposure and to shorten the time required for setting.