To provide an X-ray CT apparatus allowing acquisition of a photographing range without needing scanography, and without increasing cost.

The X-ray CT apparatus introducing a top plate on which a test subject is placed into a base and photographing the test subject to acquire a tomographic image includes a winding shaft, a support means, and an arithmetic part. A linear member formed in a linear shape is wound around the winding shaft. The support means is provided in the base, and supports the winding shaft such that the winding shaft is inclined according to a direction to which the linear member is paid out from the winding shaft. The arithmetic part calculates the photographing range relative to the base based on a length by which the linear member is paid out and an angle by which the winding shaft is inclined when paying out the tip of the linear member from the winding shaft to the range where the tomographic image is acquired by the photographing.