An air conditioning device for a vehicle having a compressor that supplies a high-pressure refrigerant, an air heating heat exchanger heating air that is to be blown into a vehicle cabin, a pressure reduction part expanding and decompressing the high-pressure refrigerant so as to supply an intermediate-pressure refrigerant and a low-pressure refrigerant, a first low-pressure side heat exchanger exchanging heat between the intermediate-pressure refrigerant and a heating medium other than the air, a second low-pressure side heat exchanger cooling the heating medium by exchanging heat between the low-pressure refrigerant and the heating medium, a first heating medium circuit through which the heating medium cooled in the second low-pressure side heat exchanger circulates, and a heating medium-air heat exchanger.