1. An ultrasonic imaging apparatus for transmitting ultrasonic waves toward an object to be inspected and receiving ultrasonic echoes from the object to display an ultrasonic image based on the received ultrasonic echoes, said apparatus comprising: ultrasonic transmitting and receiving means for transmitting ultrasonic waves according to applied drive signals, and receiving ultrasonic echoes reflected from the object to output reception signals; signal processing means for performing signal processing on the reception signals outputted from said ultrasonic transmitting and receiving means to generate original data representing ultrasonic image information on the object; speckle image generating means for generating speckle image data representing a speckle image based on the original data generated by said signal processing means; speckle image analysis means for generating speckle analysis result image data representing a change of speckle images between adjacent two frames as a moving image based on the speckle image data generated by said speckle image generating means; and displaying means for displaying said analysis results represented by said speckle analysis result image data; wherein said speckle image generating means generates structure image data based on at least one of (i) a first signal representing local maximum points extracted from the original data and interpolation points obtained by interpolation between the local maximum points, (ii) a second signal representing local minimum points extracted from the original data and interpolation points obtained by interpolation between the local minimum points, and (iii) a third signal representing average values of the first signal and the second signal, and generates the speckle image data by subtracting values represented by the structure image data from values represented by the original data.