An ultrasound diagnostic apparatus includes: an ultrasound probe； region-of-interest setting means for setting the depth position of a region of interest in a subject； reflection point setting means for setting a plurality of points in a region, which is deeper than the depth position of the region of interest, as reflection points of ultrasound waves transmitted from the ultrasound probe； and sound speed value deriving means for deriving a sound speed value in a region between each of the plurality of reflection points and the ultrasound probe, for each of the plurality of reflection points, based on a reception signal generated when the ultrasound probe receives an ultrasound wave reflected at each of the plurality of reflection points.
