In the ultrasound diagnostic apparatus, the ultrasonic wave transmitter/receiver transmits and receives an ultrasonic beam to a subject to generate reception data the delay correction unit corrects a delay time of the reception data to align a phase of the reception data the reception aperture level setting unit sets two or more reception aperture levels of reception data from reception data after correction of the delay time the image producer produces ultrasound images corresponding to the set reception aperture levels, by performing phase matching addition on the reception data after correction of the delay time and the image quality determination unit determines image qualities of the ultrasound images corresponding to the set reception aperture levels and selects an ultrasound image having a predetermined image quality.
