Provided is an X-ray CT device with which duplicability of helical shuttle scanning can be monitored using an arbitrary reference. An X-ray CT device according to an embodiment of the present invention includes an X-ray scanning unit provided with an X-ray generation unit and an X-ray detector which scan and perform X-ray imaging with respect to a periphery of a subject positioned on a top plate. The X-ray CT device causes the X-ray scanning unit to perform X-ray imaging while causing the top plate and the X-ray scanning unit to reciprocally move relative to the subject in a first direction along the length direction of the top plate and a second direction inverse to the first direction. The X-ray CT device is provided with a comparison unit. The comparison unit compares top plate positions at points in time when prescribed view numbers are acquired, in X-ray imaging performed several times in the first direction and X-ray imaging performed several times in the second direction.