[Aim] To provide an image appropriate for observation of the course of blood vessels in a neighborhood of a cutting surface in a surgery assistance apparatus for assisting a surgery of excising an organ [Solution Means] An image generation means (70) that generates, from a three-dimensional image of an organ in which an excision region has been identified, an image representing the organ in such a manner that a blood vessel region in the organ is visually recognizable, a depth input receiving means (50) that receives an input specifying a depth of cutting, and a cutting surface setting means (60) that determines, as a cutting surface, a portion of a boundary surface within the specified depth of cutting along the boundary surface from an outer edge of the boundary surface toward an inside, and the boundary surface being between the excision region and a non-excision region, which is a region other than the excision region, in the organ, are provided. The image generation means (70) generates, from the three-dimensional image, the image representing the organ in such a manner that only a partial blood vessel region, which is present in a neighborhood region of the cutting surface in the blood vessel region of the organ, is visually recognizable.
