1. An X-ray CT apparatus comprising: a first setting device configured to set on a scout image of a subject in a lateral direction thereof, a desired reconstruction range of a tilt image based on a desired tilt angle such that the tilt image includes a region of interest of the subject; a second setting device configured to set on the scout image, a scan range for a non-tilt scan, the scan range being placed on an inner side of a range necessary to reconstruct the tilt image with respect to all scan spaces in the reconstruction range set by the first setting device, wherein the scan range includes the region of interest; a scan execution device configured to execute the non-tilt scan on the scan range set by the second setting device; and a reconstruction device configured to reconstruct the tilt image including at least the region of interest with respect to the reconstruction range set by the first setting device based on projection data acquired by execution of the non-tilt scan.