PURPOSE: To compact the size, reduce the weight, simplify the construction, and divide the operation into two strokes in one direction in which response speed is high, with regard to a shape memory alloy actuator, by balancing the elastic force of a SMA (shape memory alloy) with the energizing force of an elastic member in the course of a moving locus to stop a moving member.

CONSTITUTION: A shape memory treatment is given to a SMA coil 1 in extended condition beforehand so that it may be extended gradually after inverse transformation start temperature is passed by heating. Meantime, a plate 2 is moved against an energizing force of a bias spring 5 to force its top end 2c near a block 11 and turn on a switch 8 by means of its slant surface 2d. Since a heating circuit 10 controls the electricity passing through the coil 1 by means of the signal to keep the temperature of the oil as it is, an object 12 can be carried by moving it together with a base. In addition, when the oil 1 is energized to be heated by the circuit 10, the plate 2 moves while rotating along a cam in clockwise direction to depart its top end 2c from the block 11. Accordingly, the object 12 is unloaded at a moved location of the base, a switch 9 is turned on by means of the top end 2c to stop the supply of electricity from the circuit 10 to the coil 1, and the plate 2 is also stopped by making contact with a stopper 6.