A rotation frame supports an X-ray tube and an X-ray detector to be rotatable about a rotation axis. A top plate support mechanism supports the top plate on which a sample is placed to be movable along the rotation axis. A scan controller drives the top plate support mechanism and the rotation frame so as to scan a plurality of scan areas either partially overlapping or being adjacent along the rotation axis with the X-rays. A reconstruction processor generates a plurality of volume data sets corresponding to the plurality of scan areas on the basis of the output from the X-ray detector. A boundary corrector corrects CT values of the plurality of volume data sets on the basis of CT value differences between the overlapping or adjacent portions of the plurality of volume data sets.
