Using first voxel data of a three-dimensional medical image obtained by photographing a subject, a functional image representing a function of a heart in at least one position is generated, and using a portion of second voxel data of a three-dimensional medical image obtained by photographing the subject corresponding to an area which includes a blood vessel along an outer myocardial wall of the heart, a morphological image depicting morphology of the blood vessel is generated. Then, the functional image and the morphological image are displayed in a superimposing manner such that at least one position of the heart in the functional image corresponds to at least one position of the heart in the morphological image.