In an ultrasound diagnostic apparatus of the present invention, the controller writes and reads element data of one frame into and out from two or more buffer memories 21a, 21b, . . . 21i sequentially frame by frame and assigns the element data of one frame sequentially read out from the buffer memories to a plurality of arithmetic blocks of a signal processor, wherein the element data assigned is subjected to processing by each of a plurality of arithmetic cores in the plurality of arithmetic blocks to produce an image signal.