To provide a medical image processor capable of simply calculating intravascular blood flow information at a high speed.

A medical image processor of an embodiment includes a 2D image generation part, and a calculation part. The 2D image generation part generates a two-dimensional tomographic image of a blood vessel in which a feature of a lesioned part in a blood vessel included in three-dimensional medical image data is reflected, from the three-dimensional medical image data. Then, the calculation part calculates fluid information in the blood vessel by applying calculation hydrodynamics to the two-dimensional image generated by the 2D image generation part.