1. A diagnostic imaging apparatus comprising: an ultrasonic probe configured to transmit ultrasonic waves to a target object and acquire a reflection signal from said target object, for a plurality of image frames, which are constituted as a plurality of two-dimensional ultrasonic images acquired by said ultrasonic probe; a measuring area setting unit for setting, for each image frame, a plurality of measuring areas used for measuring a body movement of said target object, by dividing said two-dimensional ultrasonic image into said plurality of measuring areas; a body movement measuring unit for detecting movement and deformation amounts of said target object, in comparison between said measuring areas of a base image frame and said measuring areas following images frame which follow said base frame in time-series; an image accumulating/subtracting unit for accumulating or subtracting a plurality of images of the plurality of image frames after a body movement correction based on said measurement of said body movement; and an image display unit for displaying a reconstructed two-dimensional tomograph images processed by said image accumulating/subtracting unit by using said measuring areas, wherein said body movement measuring unit extracts, from said image frame, a measuring area, which is consistent with said measuring area on said following frames, and measures, as said body movement, displacement between said extracted area and said measuring area on said following frames.