PURPOSE: To reduce the number of part items and reduce the cost.

CONSTITUTION: This imaging device driving mechanism for an X-ray radioscopic photographing base moves an image device 31 in the longitudinal direction of a table support frame 3 erectably supporting a top plate 1 to position it in the living body axis direction for the X-ray fluoroscopic photographic of an examinee on the top plate 1. A driving unit 23 is provided on the imaging device 31 side, and a pinion 22 is provided on the output shaft of the driving unit 23. The pinion 22 is meshed with a rack 3c provided on the table support frame 3 in the longitudinal direction so that the imaging device 31 is self- traveled in the longitudinal direction of the table support frame 3 by the action of the driving unit 23.