When an image creating unit creates a three-dimensional ultrasound image of a blood-vessel early phase, an operator presses an image selecting button, and selects an area to be displayed as superimposed by using an image-selecting Graphical User Interface (GUI) displayed by an image-selecting GUI display-control unit. After the image creating unit start creation of a three-dimensional ultrasound image in a late phase, when the operator presses a composition display button, the movement-distance calculating unit calculates a movement distance between a three-dimensional tissue image at the moment of the press of the composition display button and each of three-dimensional tissue images in the area to be displayed as superimposed, and an image correcting unit corrects each of three-dimensional contrast enhanced images corresponding the three-dimensional tissue images of the blood-vessel early phase by using the movement distance. An animated-image compositing unit creates a group of images for animation that the corrected three-dimensional contrast enhanced images of the blood-vessel early phase are each combined with a three-dimensional contrast enhanced image of the late phase, and a monitor displays the group of the images for animation in animation.