A pre-acquired reference image, a currently picked-up ultrasonic image, and position information indicating a relation between a position of the ultrasonic probe when the reference image was picked-up and a current position of the ultrasonic probe are displayed on a display portion as navigation information. Also, when the following diagnosis image is to be acquired, probe movement information, specifying a position or the like to which the ultrasonic probe has to be moved, is displayed on the display portion as the navigation information.
