1. An X-ray CT apparatus including data acquisition equipment that scans a subject with X-rays so as to acquire projection data, and image reconstruction equipment that reconstructs an image on the basis of the acquired projection data, wherein: the image reconstruction equipment comprises: a system model construction device for constructing a system model that has a plurality of concentric rings each segmented into a plurality of sectors; a system matrix construction device for constructing a system matrix associated with one view, by using some of all the sectors constituting the system model, the some of all the sectors being located on respective projection lines concerning the one view; a system matrix creation device for creating a system matrix associated with another view, by transforming the system matrix associated with the one view; an image reconstruction device that reconstructs an image through iterative reconstruction by using the system matrix and projection data; and a transformation device for transforming the image into an image composed of rectangular pixels.