An image processing apparatus according to an embodiment includes storage circuitry and processing circuitry. The storage circuitry stores therein fluid resistance data representing a correlation among a vascular shape, a blood flow rate, and a pressure loss. The processing circuitry extracts, from three-dimensional image data in which a blood vessel of a subject is rendered, vascular shape data representing a shape of the blood vessel. The processing circuitry performs fluid analysis based on the vascular shape data and the blood flow rate and the pressure loss that correspond to the vascular shape data and that are correlated by the fluid resistance data to derive a functional index related to a blood circulation state in the blood vessel of the subject.
