An X-ray CT apparatus includes an image generating unit, a discrimination unit, a monochromatic X-ray image generating unit, a combined-image generating unit and a display unit. The image generating unit generates a plurality of reference material images corresponding to respective ones of a plurality of reference materials on a basis of pre-reconstruction data of multi-energy obtained by scanning a subject. The discrimination unit discriminates each of a plurality of materials contained in an imaging region of the subject on a basis of the plurality of reference material images. The monochromatic X-ray image generating unit generates a monochromatic X-ray image at energy determined by each of the plurality of discriminated materials. The combined-image generating unit combines a plurality of monochromatic X-ray images corresponding to the plurality of materials and to generate a combined image. The display unit displays the combined image on a display device.
