A target place is set in an area of a human body structure having a tree structure in a three-dimensional image. The tree structure of the human body structure is extracted. A path from a reference point set on a branch upstream side of the target place on the tree structure to the target place is determined. Priority is set for respective portions of the tree structure of the human body structure outside the path based on a positional relationship between the portions and the target place. An initial image representing only a portion of the path and images for confirmation of each step sequentially representing the respective portions of the human body structure outside the path according to the priority are generated from the three-dimensional image. The initial image is displayed, and then, the generated images for confirmation of each step are displayed.
