1. An ultrasonic imaging apparatus comprising a transmitter for transmitting ultrasonic waves directed to an object, a receiver for receiving the ultrasonic waves coming from the object, and a processor for processing received signals of the receiver to generate an image made up of two or more frames, wherein, the processor assumes one frame as a reference frame, in the image made up of two or more frames being generated, sets a region of interest at either of a predetermined position and a position accepted from an operator, assumes another one frame as a comparative frame, sets a search area wider than the region of interest, at either of a predetermined position and a position accepted from an operator, sets in the search area, multiple candidate regions which are destination candidates of the region of interest, calculates a degree of similarity of an image characteristic value between in the region of interest and in the candidate region, with respect to each of the candidate regions, so as to obtain a similarity distribution of the degrees of similarity across the search area.