PURPOSE: To obtain an engine of high efficiency and simple structure by making it possible to electrify through the deflected member of a shape memory alloy, which is deflected at a low temperature at the fixed side, to a catching member provided on a rotating body connected to a load.

CONSTITUTION: A deflected member 5 is under a low temperature condition causing deflection by force of a spring 6. When a rotating body 1 is rotated towards the arrow direction, a catching member 3 comes in contact with the deflected member 5 and goes into a caught condition. Electricity starts running through both members as soon as the members come into contact with each other. The temperature of the deflected member 5 then rises and tries to return to its original shape, that is, a straight shape, causing the catching member 3 to be pushed out towards the circuit direction and give a rotating drive to the rotating body 1. After the catching member 3 is pushed out, it is separated from the deflected member 5 and the electrification through the two members stops causing the temperature of the deflected member 5 to drop and the deflection to start again. The rotation of the rotating body 1 is continued by repeating this cycle. Further, it is possible to increase the output by using plural number of a catching member and a deflected member.