PURPOSE: To give a temperature variation to a form memory alloy and make power securable, by injecting two types of liquids being hard to mixed and different in specific gravity, having an interface, into a vessel, while keeping up such temperature as causing both liquids to become up and down of a transformation point (temperature) of the form memory alloy inside the vessel, and moving the interface up and down.

CONSTITUTION: When warmed oil 3 being different in specific gravity and hard to be mixed and cooled water 4 are poured into a vessel housing a wire 1 of a form memory alloy to be deformed into a spring form at a transformation point, the upper liquid 3 is kept up more than transformation temperature while the lower liquid 4 below that temperature, respectively, whereby an interface as in illustration is formed with their specific relations. Accordingly, when a bellows part 5 is pulled down, the warmed oil 3 enters inside from the upside whereby the wire made of the form memory alloy is formed into a coil form, while pulling a crank 7 and rotating a generator 9. When the crank 7m reaches the lower end and the cooled water 4 is taken in from the downside after pushing the bellows 5, the interface goes up, and simultaneously an inertia by a flywheel 8 stretches a cooled coil. Afterward, operation as aforesaid is repeated whereby the power required is securable so speedily and economically.