An ultrasound diagnostic apparatus including an ultrasound probe configured to transmit toward and receive from a three-dimensional region of a subject, a transmitting and receiving unit configured to acquire ultrasound data by a plurality of executions of multibeam forming, comprising forming a plurality of sets of ultrasound data along a plurality of directions by a one-time transmitting and receiving operation of the ultrasound probe, a data synthesizing unit configured to synthesize a plurality of sets of data relating to the ultrasound data acquired during each of said executions, the sets being acquired along a respective plurality of different receiving directions with respect to a transmitting direction, to generate synthesized ultrasound data, and an image data generation unit configured to generate image data on the basis of the synthesized ultrasound data.
