An air conditioner, comprising: a refrigerant circuit configured by the interconnection of a compressor, a heat source side heat exchanger, an expansion mechanism (38, 41, 51), and a utilization side heat exchanger (42, 52); a refrigerant quantity calculating means configured to divide the refrigerant circuit into a plurality of portions, to calculate the refrigerant quantity for each divided portion, and thereby calculate the refrigerant quantity in the refrigerant circuit; wherein the refrigerant quantity calculating means is configured to calculate the refrigerant quantity in the refrigerant circuit taking into account a dissolved refrigerant quantity that is the quantity of refrigerant dissolved in the refrigerating machine oil in the compressor, based on an operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit; and the air conditioner further comprising a refrigerant quantity judging means configured to judge the adequacy of the refrigerant quantity in the refrigerant circuit based on the refrigerant quantity calculated by the refrigerant quantity calculating means, characterized in that: the refrigerant quantity calculating means is configured to calculate the dissolved refrigerant quantity based on operation state quantities that at least include the ambient temperature outside the compressor; wherein the operation state quantities used for calculating the dissolved refrigerant quantity further include the temperature of the refrigerant in contact with the refrigerating machine oil in the compressor or an operation state quantity equivalent to the temperature. a refrigerant circuit configured by the interconnection of a compressor, a heat source side heat exchanger, an expansion mechanism (38, 41, 51), and a utilization side heat exchanger (42, 52); a refrigerant quantity calculating means configured to divide the refrigerant circuit into a plurality of portions, to calculate the refrigerant quantity for each divided portion, and thereby calculate the refrigerant quantity in the refrigerant circuit; wherein the refrigerant quantity calculating means is configured to calculate the refrigerant quantity in the refrigerant circuit taking into account a dissolved refrigerant quantity that is the quantity of refrigerant dissolved in the refrigerating machine oil in the compressor, based on an operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit; and the air conditioner further comprising a refrigerant quantity judging means configured to judge the adequacy of the refrigerant quantity in the refrigerant circuit based on the refrigerant quantity calculated by the refrigerant quantity calculating means, the refrigerant quantity calculating means is configured to calculate the dissolved refrigerant quantity based on operation state quantities that at least include the ambient temperature outside the compressor; wherein the operation state quantities used for calculating the dissolved refrigerant quantity further include the temperature of the refrigerant in contact with the refrigerating machine oil in the compressor or an operation state quantity equivalent to the temperature.