1. A medical image processing apparatus comprising: a storage unit configured to store three-dimensional function image data concerning a function index of a heart; a first extraction unit configured to extract a myocardial region from the three-dimensional function image data; a normalization unit configured to normalize a distance between an inner wall and outer wall of the myocardial region with a predetermined numerical value range associated with a thickness direction; a bull's eye map generation unit configured to generate a bull's eye map expressing a spatial distribution of pixel values at positions on the myocardial region by two-dimensional polar coordinates, the positions corresponding to predetermined values in the predetermined numerical value range; a designation unit configured to designate the predetermined values within the predetermined numerical value range, which is associated with the thickness direction, in accordance with an instruction from a user; and a display unit configured to display the bull's eye map.