An image generating unit generates a medical image. A deciding unit detects a reaching time at which a contrast agent has reached a predetermined region of the medical image. The deciding unit sets a color map in which the reaching time is associated with a hue based on a first inflow time corresponding to a first designation region set to the medical image and a second inflow time corresponding to a second designation region. A generating unit generates a hue conversion image in which a hue is allocated to each region of the medical image based on the color map and the reaching time in each region of the medical image. A control unit displays the hue conversion image through a monitor.