A storage unit stores volume data including a blood vessel region. An extracting unit extracts the blood vessel region from the volume data. A specifying unit specifies a position of a region of interest in the blood vessel region and a deflection direction of a blood vessel region included in the region of interest. A determining unit determines a viewing position and a viewing direction based on the position of the region of interest and the deflection direction. A generating unit generates image data concerning the viewing position and the viewing direction based on the volume data. A display unit displays an image represented by the image data.