An X-ray CT apparatus includes an X-ray detector that is asymmetrically disposed with respect to an irradiation axis of an X-ray and first and second ends that are disposed close to and far from the irradiation axis of the X-ray, respectively. When a scanogram of an object is imaged in one direction only, a part of the object at the first end is missed. Accordingly, scanograms are imaged in first and second directions that are opposite to each other, and then the imaged scanograms are superimposed. The superimposed scanogram is used as an image for setting a scanning range. According to this configuration, although a scanogram is produced by an X-ray CT apparatus having an asymmetrically disposed X-ray detector, it is possible to produce a desired projection data by obtaining scanogram data in the opposite two directions and combining each data. As a result, the accuracy in setting of a scanning position is not deteriorated. |