The springs is called one of the oldest tools that the human race invented. A variety of kinds of springs are used in our life,and the one indispensable as one of the machine elements. After the shape memory effect with the Ti-Ni alloys is discovered, a variety of applied products are developed,and have been put to practical use until today. It introduces the application of the shape memory alloy coil springs used by the shape memory effect as thermal actuator.