To suitably perform beam hardening correction when generating tomograms by dual energy photographing.

On the basis of the ratio of the CT values of corresponding pixels between two kinds of tomograms different in X-ray tube voltage in photographing, a material image corresponding to a predetermined material in the tomograms is extracted (S3), and the extracted material image is virtually projected again (S4). Obtained re-projection data are worked according to the kind of the material and the X-ray tube voltage in photographing (S5), and image reconstitution is performed on the basis of the worked re-projection data (S6). The original tomogram and the newly obtained new material image are subjected to weighted addition to generate a new tomogram (S7). Consequently, the image of the material to be corrected is extracted precisely, and beam hardening correction suitable to the image is suitably performed.

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