There is disclosed an air conditioning device of a so-called heat pump system which efficiently and comfortably heats a vehicle interior. In a vehicle air conditioning device 1, a controller executes a heating mode in which a refrigerant discharged from a compressor 2 radiates heat in a radiator 4 and the refrigerant by which heat has been radiated is decompressed and then absorbs heat in an outdoor heat exchanger 7. The vehicle air conditioning device includes a heating medium circulating circuit 23 to heat air to be supplied from an air flow passage 3 into the vehicle interior, and the controller executes the heating by a heating medium-air heat exchanger 40 of the heating medium circulating circuit 23, when a heating capability by the radiator 4 runs short.