PROBLEM TO BE SOLVED: To secure the desired freezing efficiency in spite of a simple constitution. SOLUTION: This air conditioner comprises a freezing cycle 1 for circulating a refrigerant discharged from a compressor 2, to the compressor 2 through a vehicle outer side heat exchanger 3, a refrigerant decompressing means 4 and a vehicle inner side heat exchanger 5. An internal heat exchanger 6 is mounted for exchanging the heat between a high-pressure part where the refrigerant flows from the vehicle outer side heat exchanger 3 toward the refrigerant decompressing means 4, and a low-pressure part where the refrigerant flows from the vehicle inner side heat exchanger 5 toward the compressor 2. Oil separating means 18 - 21 for separating the oil from the refrigerant flowing in the high-pressure part, and oil decompressing means 22, 23 for decompressing the oil separated by the oil separating means 18 - 21 and circulating the same to the low-pressure part are integrally mounted on the internal heat exchanger 6. COPYRIGHT: (C)2004,JPO&NCIPI