In order to provide an ultrasonic diagnostic apparatus and a sound speed correction method capable of performing sound speed correction without affecting real-time efficiency, the present invention is characterized in that a reference sound speed image signal is acquired by setting a reference sound speed and a different sound speed image signal is acquired by setting a different sound speed from the reference sound speed and that sound speed correction information is acquired by correcting reference sound speed information based on the reference sound speed image signal using different items of sound speed information based on the different sound speed image signal.
