According to an embodiment, an X-ray computed tomography (CT) apparatus includes processing circuitry. The processing circuitry is configured to acquire projection data that is based on a spectrum representing an amount of X-rays with respect to energy of a radiation having passed through a subject select a plurality of materials generate, from the projection data, first density images for each of the selected materials generate a monochromatic image of specific energy from the first density images reconstruct the projection data corresponding to the specific energy to generate a reconstructed image compare the monochromatic image and the reconstructed image and provide a notification indicating a result of the comparison.
