Information of constituent substances of an object is reconstructed with high accuracy without being influenced by a decrease in measurement accuracy even if measurement in which a tube voltage is changed is not performed. A CT apparatus includes: a detection unit configured to obtain measurement information based on a detection result of radiation irradiated based on a constant tube voltage an obtaining unit configured to obtain second measurement information of the radiation based on a moment of the measurement information obtained by detecting the radiation a plurality of times a classification unit configured to classify an object into a plurality of substances and a reconstruction unit configured to reconstruct the information of the constituent substances of the object based on the second information.
