An air conditioner includes a refrigerant circuit, an operation controlling section, a stability judging section, a refrigerant quantity judging section, and a condition changing section. The operation controlling section is capable of performing a refrigerant quantity judging operation to control constituent equipment to reach a predetermined target control value. The stability judging section judges whether or not the refrigerant quantity judging operation has stabilized. The refrigerant quantity judging section judges the adequacy of the refrigerant quantity in the refrigerant circuit by using an operation state quantity of constituent equipment or refrigerant flowing in the refrigerant circuit when it is judged that the refrigerant quantity judging operation has stabilized. The condition changing section changes the target control value in the refrigerant quantity judging operation when it is judged that the refrigerant quantity judging operation has not stabilized.