A CT apparatus includes: a tube that produces an X-ray photon whose highest energy is higher than highest peak energy of characteristic X-rays a detecting material a unit that produces a first attenuation coefficient map which corresponds to a first energy region including the highest peak energy of the characteristic X-rays a unit that transforms the first attenuation coefficient map into a second attenuation coefficient map of a second energy region a unit that produces a scattered photon distribution of scattered X-ray photons on the basis of the second attenuation coefficient map and a unit that produces data before reconstruction on the basis of the detected X-ray photon which corresponds to the second energy region, corrects and processes the data before reconstruction with the scattered photon distribution so as to produce corrected data, and reconstructs an image corresponding to the second energy region for which scattered radiation is corrected.
