PURPOSE: To improve operability by facilitating rotary operation and position setting of a holding device.

CONSTITUTION: When a holding device 1 is rotated, a detecting switch 6 detects this rotation, and outputs a detecting signal corresponding to positional dislocation of a cassette 3. This detecting signal is inputted to a motor, and the holding device 1 is moved so that height of a mamma in a head tail direction and height of the mamma in an inward and outward direction coincide with each other. Since height dislocation of the cassette 3 to the mamma caused by rotation of the holding device 1 can be corrected, even if a photographing direction is changed, an operator can set a device easily, so that operability and diagnostic efficiency can be improved.