When a subject is pressed by a plate and an acoustic wave is received by a probe via the plate, the acoustic wave is refracted because of the difference between a sound velocity in the subject and a sound velocity in the plate. When the refraction is not considered, a reduction in resolution occurs. A correction table or a correction formula for correcting image distortion associated with refraction is provided. After image information is acquired, new image information is acquired in accordance with the correction table or the correction formula, and is displayed.
