An X-ray CT apparatus permitting compatibility between the resolution orientation and the coverage orientation at low cost is to be realized. The X-ray CT apparatus uses as the X-ray detector what has a former half channel part and a latter half channel part which are the same in the number of slices and differ in the coverage in the body axis direction of the subject and in slice thickness, and selectively performs scan control in the high resolution mode in which the coverage and the slice thickness are smaller and scan control in the high coverage mode in which the coverage and the slice thickness are larger.