PURPOSE: To provide an air conditioning device which is capable of increasing a power shift capacity during day time power peak, and what is more, carrying out effective heat accumulating operation even during heating time.

CONSTITUTION: A heat storage tank 43, which is capable of accumulating the heat of refrigerant circulating in a refrigeration cycle is installed to the refrigeration cycle which comprises a compressor 21, an outdoor heat exchanger 25, an expansion valve 31 and an indoor heat exchanger 27, which are all connected to a refrigerant pipeline 33. A heat storage refrigerant pipeline 39 which distributes the refrigerant to be heat-exchanged between a heat accumulating material inside the heat storage tank 43, is laid out in parallel to the indoor heat exchanger 27. An auxiliary compressor 47 is installed to the heat storage refrigerant pipeline 39 between the heat storage tank 43 and a gas line of the refrigerant pipeline 33.