In an X-ray CT imaging, an X-ray generator (11) and a two-dimensional X-ray detector (21) are opposed to each other between an object and are rotated by a rotary shaft (32) around the object. At least one of the rotary shaft supporter (61) and an object holder (40) includes a movement mechanism (42, 65) for moving a supporter (30) for the X-ray generator and the X-ray detector relative to the object. In offset scan CT imaging, the rotation of the supporter by the rotary shaft is performed simultaneously with the relative two-dimensional movement of the rotary shaft by the movement mechanism. In the relative two-dimensional movement, the position of the rotary shaft is moved according to the rotary angle of the supporter along a circular orbit around the center of a CT imaging region in a plane crossing the rotary shaft. Thus, it becomes possible to image a larger region of interest of the object.