Abstract: A scanning device for use in axial transverse tomographic apparatus, arranged so that a support which carries thereon an X-ray source and its associated detector is mounted on a rotary disk for reciprocating linear movements, and that this rotary disk is caused to rotate through a certain angle at a time for each change of direction of the linear movements of the support. The support is moved at a plurality of different speeds. Either a single or a plurality of damping means are arranged so as to reduce the speed of movement of the support and then to accelerate this speed in association with the movement speed thereof at any changing of direction of movement of this support.