To provide a power generating system capable of recycling the waste heat of ordinary temperature level which is abandoned in a conventional system.

This temperature difference cycling power generating system comprises a high temperature source and a low temperature source opposite to each other, a variable capacitance capacitor composed of a fixed electrode and a movable electrode movable by a spring, a bias power source, and a transformer for deriving the power. The variable capacitance capacitor is mounted between the high temperature source and the low temperature source, in such manner that it can transfer the heat to the high temperature source or the low temperature source. The bias power source and the transformer are electrically mounted between the fixed electrode and the movable electrode of the variable capacitance capacitor. The variation of the capacity of the capacitor caused by the movement of the heat through a variable electrode, and the motion of the movable electrode induced by the variation of a spring constant or condition of the spring in accompany with the movement of the heat is derived from the transformer as the power.