For measurement of minute change in thickness using ultrasound, the phase tracking method based on the constraint least-squares approach has been developed. The value measured by this method has the order of sub-micrometer, and it is difficult to verify the precision of the value. We fabricated a novel phantom, which consisted of materials in consideration of the acoustic and the optical characteristics. The thickness of the phantom changed periodically and the change was measured by the ultrasound and laser simultaneously. We evaluated proposal ultrasound measurement system with the value measured by the laser. From the experimental results, it was obtained that our ultrasound measurement system had an accuracy of about 0.2 μm.