A tomographic image processing apparatus includes a data acquisition interface configured to acquire raw data; a memory; and at least one processor configured to: obtain, from the memory, a first partial reconstruction image corresponding to a partial angular range of a first rotation period of an X-ray generator; generate a second partial reconstruction image from partial raw data acquired in a partial angular range of a second rotation period of the X-ray generator, wherein the partial angular range of the first rotation period corresponds to the partial angular range of the second rotation period; generate a third partial reconstruction image based on the first partial reconstruction image and the second partial reconstruction image; store the third partial reconstruction image in the memory; and generate a resultant image based on the third partial reconstruction image and a plurality of partial reconstruction images stored in the memory.