Abstract: A computed tomography system includes an image reconstruction data generator for generating image reconstruction data for a desired slice plane of an object in accordance with measuring projection data, the image reconstruction data being obtained from measuring projection data obtained at each of a plurality of rotation positions of a radiation source, and an image reconstructor for obtaining tomographic image data of the object for the desired slice plane in accordance with the image reconstruction data. The image reconstruction data generator has the capability of grouping the measuring projection data into a plurality of groups respectively corresponding to a plurality of desired slice planes of the object, the desired slice planes being spaced apart from each other by a distance corresponding to one rotation position of the radiation source, with each of the groups corresponding to a continuous rotation range of 360.degree.