PURPOSE: To provide a miniature and light weight apparatus. and ensure secure operation of a whole freezing cycle and hence improve thermal efficiency by making use of waste heat of an engine as a driving heat source without the need of using a motor using electricity as a driving source for starting a displacer of the freezing cycle, and selecting an optimum driving method in response to the conditions of the freezing cycle.

CONSTITUTION: Taking notice of using driving force and waste heat of an engine 3 as a driving source of a displacer 10, there are provided heat exchge means (waste gas heat exchange means 2) for exchanging heat as a heat source of the engine 3, and driving force changeover means 5 provided between the displacer 10 and an output part 4 of the engine 3. In the early time of starting of a freezing cycle, the freezing cycle is driven by the output part 4 of the engine 3, and after the starting it is driven by energy of a heat source (waste gas) heat exchanged by the heat exchange means 2.