A three-dimensional common coordinate system is defined and a first correspondence relationship between each pixel of a first three-dimensional image which has at least a portion of a human body as a subject and coordinates on the common coordinate system is set. A second three-dimensional image which has at least a portion of the human body as a subject that at least partially overlaps the subject in the first three-dimensional image is aligned with the first three-dimensional image to calculate a correspondence relationship between pixels of the first three-dimensional image and the second three-dimensional image. A second correspondence relationship between each pixel of the second three-dimensional image and coordinates on the common coordinate system is calculated on the basis of the calculated correspondence relationship and the set first correspondence relationship. The first correspondence relationship and the second correspondence relationship are stored.
