An image processing apparatus according to an embodiment includes processing circuitry. The processing circuitry is configured to acquire pieces of change information indicating temporal changes in computed tomography (CT) values of a myocardium and a right ventricular of a subject based on a plurality of chronologically consecutive images that are generated by an X-ray CT apparatus by scanning the subject to which a contrast agent is administered. The processing circuitry is configured to correct the piece of change information on the myocardium based on the piece of change information on the right ventricular.