An X-ray CT scanner includes a projection-data acquisition unit for
acquiring projection data for the three-dimensional region of a subject,
an input unit for setting a section in a desired direction in the
three-dimensional region in accordance with the instruction of an
operator, a reconstruction-region calculation circuit for specifying a
plurality of reconstruction portions intersecting the set section, a
reconstruction arithmetic circuit for reconstructing a plurality of
partial images for the specified reconstruction portions on the basis of
the projection data, and an image-data processing circuit for generating
an image for the set section on the basis of the plurality of
reconstructed partial images.