An ultrasound diagnostic apparatus is provided which includes an ultrasound probe performing ultrasound transmission and reception in different directions and a diagnostic apparatus body combining images different in the direction of transmission and reception to produce an ultrasound image. At least one of ultrasound images to be combined is changed depending on the set region of interest (ROI) to an image of the depth corresponding to the ROI. When an acoustic coupler is attached, the depth of at least one of ultrasound images to be combined is increased. The ultrasound diagnostic apparatus is capable of improving the image quality of the ROI and obtaining efficient high-definition ultrasound images reaching a predetermined depth when the acoustic coupler is attached.
