Ultrasonic image data from a plurality of time phases are stored in an image storage unit (22). A pattern matching unit (30) searches the image data in a search time phase for moving points corresponding to set points in the image data in a reference time phase, on the basis of a correlation operation performed on the image data. In this way, moving points for set points are searched across a plurality of time phases. A diagnostic information generating unit (40) then determines the main direction of movement of the set points across the plurality of time phases based on the moving points searched across the plurality of time phases, and diagnostic information is obtained by evaluating the movement of the set points with reference to the main direction.