In order to obviously visualizing a characteristic of a tubular structure in a three-dimensional image, an index value calculation unit (33) calculates an index value representing a characteristic of a tubular structure extracted from a three-dimensional medical image in each direction of radial visual lines orthogonal to a core line of the tubular structure at each of a plurality of points on the core line with each point as each viewpoint and a map image generation unit (34) generates a characteristic map image representing the characteristic inside of the tubular structure by mapping the index value calculated in each direction of the radial visual lines at each point on the core line to a coordinate plane defined by a first coordinate component representing a position in a direction of the core line and a second coordinate component representing a direction of each visual line.
