Extracting a tubular structure from volume data, determining a target region which should be reached by an endoscope through the tubular structure, extracting, among plurality on a route of the tubular structure, a point that satisfies a given condition as a target point that should be reached by a distal end portion of the endoscope, and identifying and determining a route of the tubular structure from a predetermined start point in the tubular structure to the extracted target point as a route through which the endoscope should be passed.