PURPOSE: To obtain a sectional image without any blur and artifact by one time scan by interpolate projection data so as to generate a vertical sectional image in a vertical sectional image generation step, and generating a virtual sectional image without any interpolation process in a virtual sectional image generation step.

CONSTITUTION: Two kinds of images, that is, a vertical section and a virtual section approximating the section are generated, in a step 4 and a differential image comprising a blur and an artifact of an image due to interpolation operation where a vertical sectional image and a virtual sectional image may not cancel each other is generated. In a step 5, the blur and the artifact of the image due to interpolating operation are separated in the differential image. In a step 6, so as to remove the blur of the image due to interpolating operation from the vertical sectional image to obtain a vertical sectional image, without any blur in a step 7 and the artifact is removed from the virtual sectional image to obtain a virtual sectional image without any artifact.