An image generation method of an interior CT includes the following steps: a step for obtaining interior CT projection data by measuring only all of quantum beams passing through a region of interest (ROI) in an inside of photographing object in a geometrical system for CT measurement； a step for obtaining partial entire projection data by measuring quantum beams passing through an entire of said photographing object from a segment in an outside of said photographing object in said geometrical system for CT measurement； and a processing step for exactly reconstructing said ROI upon basis of said interior CT projection data obtained and said partial entire projection data.
