<p>Various buoyancy control methods of underwater system have been proposed and developed. In this study, we tried to develop smaller, lighter and better response unit and conducted experimental examination. We proposed a buoyancy control method by changing the volume by pulling a rubber membrane with shape memory alloy actuator that is manufactured an experiment unit. We tried to measure the unit behavior that is changed according to the applied voltage and the shape of input voltage signal. As a result, we confirmed that we can change the buoyancy by changing input voltage signal, and found out that input voltage and buoyancy had a correlation.</p>