According to one embodiment, an X-ray CT apparatus includes an energy classifying unit, a setting unit, and an image generating unit. The energy classifying unit is configured to classify photons passing through an object into a number of energy bins in accordance with energy of the photons. The setting unit is configured to set an energy level and set an energy width of a plurality of energy bins of the number of energy bins. The image generating unit is configured to generate an extended energy bin image based on information on the photons classified into the plurality of energy bins, the image having the energy level and the energy width of the plurality of energy bins.
