To provide an air conditioning heat pump system capable of improving cooling efficiency and heating efficiency by reducing the number of components for easily performing manufacture and construction works.

A well case 21 is provided in the ground, and a lid body 24 is suitable for an upper end opening part of the well case 21. A drain pipe 27 is connected to a well pump 26. A compressor 12, an indoor heat exchanger 15, and an expansion valve 17 are connected to a heating medium gas circulation pipe P. A heat exchanging pipe 23 serially connected so as to compose a part of the heating medium gas circulation pipe P is stored in a water storage chamber 21a of the well case 21. In a state of high-load heating operation, a detected value of a first temperature sensor 33 connected to the heating medium gas circulation pipe P is compared with a set value set beforehand in the storage medium. If the detected value is as large as or smaller than the set value, the well pump 26 is driven to pump up well water at lowered temperature in the water storage chamber 21a of the well case 21 so as to take ground water with the temperature higher than the well water into the water storage chamber 21a.