To provide a CT apparatus which enables penetrative examination of even an object comprising heavy metal or a large construction and clear detection of difference or the like of material inside.

An object S to be measured is irradiated with neutron rays 15 and an energy spectrum of neutrons passing through the object S to be measured is sampled to generate a CT image for each of a plurality of energy sections. The X rays and γ rays are limited in specificity to material whereas diversified reaction with various nucleuses is made possible by the use of the neutrons. It is already noted that the identification between substances of closer atomic numbers is very difficult by an X-ray CT apparatus or γ ray CT apparatus. But when neutrons are used in the manner as mentioned above, the neutrons passing through the object S to be measured are distinguished and analyzed by the energy thereof to enable clear identification of numerous substances. The high penetrability of the neutrons as compared with the X rays and rays also enables the detection of a larger object than ever or an internal structure, a defect or the like of an object containing heavy metal such as cadmium or boron.