A structure extracting unit extracts a structure from a three-dimensional medical image, and a view point determining unit determines a view point position and a direction of line of sight of a virtual endoscopic image. An image generating unit calculates a distance between the view point position and the extracted structure, changes an opacity defined in a color template depending on the distance, and generates, from the three-dimensional medical image, a virtual endoscopic image containing the structure shown according to the color template with the changed opacity viewed from the view point position in the direction of line of sight. A display control unit displays the thus generated virtual endoscopic image on a WS display.
