Abstract: A turntable drive unit of a microwave oven which comprises a spring box disposed below floor of the cooking chamber in the microwave oven, the spring box containing a shape memory alloy plate spring disposed therein, an axle mounted to the spring box through one end thereof and the other end thereof mounted to a food platform, and a shape memory alloy coil spring disposed in the spring box, one end of the coil spring connected to an air control plate disposed in the spring box whereby the food plateform can be automatically rotated by varying the temperature in the cooking chamber in the microwave oven and varying the temperature in the spring box.