Provided herein is an air conditioner in which the acid scavenger in a refrigeration cycle is maintained over extended time periods of operation to improve reliability. The air conditioner includes a compressor 11 for compressing a refrigerant, an outdoor heat exchanger 13 for causing a heat exchange between the refrigerant and outdoor air, an indoor heat exchanger 31 for causing a heat exchange between the refrigerant and indoor air, and an expansion valve for decompressing the refrigerant. The compressor 11, the outdoor heat exchanger 13, the indoor heat exchanger 31, and the expansion valve are connected to one another with pipes to constitute a refrigeration cycle. The air conditioner uses a refrigerator oil that uses a polyol ester oil as a base oil, and that contains an alkyl glycidyl ether compound having an epoxy group.