PURPOSE: To compact the size, reduce the weight, simplify the construction, and to reduce power consumption even in long period operation with regard to a shape memory alloy actuator by heating a pair of SMA(shape memory alloys) one by one to move a click mechanism and then terminating the heating of the SMA.

CONSTITUTION: A shape memory treatment is given to an SMA coil 1 is contracted condition beforehand so that it may be contract gradually after inverse transformation start temperature is passed by heating. Thereafter, when a switch 8 is turned off and a switch 9 is turned on, a heating circuit 10 stops to, pass electricity through the coil 1 by means of the turn on signal. An SMA coil 2 is energized to be heated by a heating circuit 11 in order to make a completely reverse action turn this state. Thus, after a pair of SMA coils 1 and 2 are heated one by one to move the click movement mechanism of a plate 3 by a click spring 5, the heating of the coils 1 and 2 is stopped to maintain its present position by the energizing force of the click spring 5. By this, power consumption can be reduced to the required minimum and, even when the temperature of the SMA coil is lowered, the operating condition can be maintained.