To easily perform positioning at the time of fluoroscopic photographing by making a recursive filter factor adjustable to one which is suitable for the movement of an arm.

When the movement of a C-shaped arm or an arm supporter is detected, the factor K of a recursive filter is made a second factor which is smaller than a first factor at the time of fluoroscopic photographing, and therefore, although noises increase in an image, an afterimage which occurs on an image being fluoroscopically photographed by the movement can be eliminated. Therefore, a photographer can easily perform positioning while watching an fluoroscopic image. Also, when the release of an electromagnetic lock 21 is detected, the factor K of the recursive filter is switched with the release as a trigger, and the recursive filter processing can automatically be switched to a suitable one by interlocking with the movement of the arm.