An air conditioner includes a refrigerant circuit, a refrigerant quantity calculating section, and a refrigerant quantity judging section. The refrigerant circuit is configured by the interconnection of a compressor, an outdoor heat exchanger, and an indoor heat exchanger. The refrigerant quantity calculating section uses a relational expression between the refrigerant quantity in each portion of the refrigerant circuit when the refrigerant circuit is divided into a plurality of portions and an operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit in order to calculate the refrigerant quantity in each portion from the operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit. The refrigerant quantity judging section uses the refrigerant quantity in each portion calculated by the refrigerant quantity calculating section in order to judge the adequacy of the refrigerant quantity in the refrigerant circuit.