Abstract: The present invention proposes a C-type arm device which has improved operational and rotational performance, a relevant C-type arm holding device and an X-ray diagnostic device employing said C-type arm holding device. The inventive C-type arm device comprises a base, a cantilever bracket, a C-type arm holding part and a C-type arm. The cantilever bracket is provided on the base at one end. The C-type arm holding part is provided on the other end of the cantilever bracket and is connected to it in such a way that the part is rotatable about a vertical axis. Said C-type arm and said C-type arm holding part are connected to each other in such a way that the arm is slidable along a circular arc of itself.