In order to display a part being observed in ultrasonic scanning within a body cavity clearly and a desired section easily, ultrasonic wave is scanned and is obtained in the body cavity. Then, an ultrasonic image creating unit creates an ultrasonic image therefrom. A schematic diagram data creating unit extracts schematic diagram data read from a schematic diagram data storing unit based on the attitude/position signal indicating the attitude of an object and the position for scanning ultrasonic wave in the body cavity, which are obtained from a position/orientation detecting unit. An image synthesizing unit synthesizes the ultrasonic image created by the ultrasonic image creating unit and the schematic diagram data created by the schematic diagram data creating unit. Then, a display displays the ultrasonic image and the schematic diagram corresponding to the position for scanning ultrasonic wave on the same screen.
