Provided is an X-ray CT device capable of controlling the scan speed while keeping the pitch of a helical scan constant. In the control of the helical scan of an X-ray CT device (1), a main control unit (5) changes the speed of a table (33) of a bed (3) during the progress of the scan and then changes the rotating speed of a gantry (2). At this time, the table moving speed and the gantry rotating speed are controlled so that the pitch is kept constant. For example, the main control unit (5) monitors the flow of a contrast medium injected into a subject (6) and changes the speed of the bed (3) or the gantry (2) according to the result thereof while keeping the beam pitch. Alternatively, the table moving speed and the gantry moving speed may be changed at a preplanned speed change position. Even in this case, the table moving speed and the gantry rotating speed are controlled so that the pitch is kept constant.
