[Object] Providing an interior CT image generation method for enabling the image reconstruction at high accuracy through the exact solution even in the case where the prior information cannot be used, i.e., being high in multiplicity of use.[Solving Means] An image generation method of an interior CT, comprising 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； and 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； wherein further including a processing step for exactly reconstructing said ROI upon basis of said interior CT projection data obtained and said partial entire projection data.
