An ultrasound diagnostic apparatus performs transmission and reception of ultrasonic waves for forming focal points used to set sound velocities at predetermined timing such that sound velocities having been set for all of respective segment regions established by diving a subject are all reset every predetermined number of frames. Owing to this configuration, it becomes possible for the ultrasound diagnostic apparatus to suitably reset sound velocities of ultrasonic waves in the subject and also reduce the amount of calculation for resetting sound velocities.
