An air conditioner, comprising: a refrigerant circuit configured by the interconnection of a compressor, a heat source side heat exchanger, an expansion mechanism (41, 51), and a utilization side heat exchanger (42, 52); operation controlling means capable of performing a refrigerant quantity judging operation to control constituent equipment to reach a predetermined target control value; stability judging means configured to judge whether or not the refrigerant quantity judging operation has stabilized; a refrigerant quantity calculating means configured to calculate a refrigerant quantity in the refrigerant circuit; and refrigerant quantity judging means configured to judge 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; characterized in that the air conditioner further comprises: condition changing means configured to change the target control value in the refrigerant quantity judging operation when it is judged that a refrigerant quantity judging operation has not stabilized; and that the stability judging means is configured to judge that the refrigerant quantity judging operation has not stabilized when a state in which a pressure of the refrigerant at a discharge side of the compressor or an operation state quantity equivalent to the pressure does not satisfy a predetermined high pressure condition or a state in which a pressure of the refrigerant at a suction side of the compressor or an operation state quantity equivalent to the pressure does not satisfy a predetermined low pressure condition continues for a predetermined period of time or longer. a refrigerant circuit configured by the interconnection of a compressor, a heat source side heat exchanger, an expansion mechanism (41, 51), and a utilization side heat exchanger (42, 52); operation controlling means capable of performing a refrigerant quantity judging operation to control constituent equipment to reach a predetermined target control value; stability judging means configured to judge whether or not the refrigerant quantity judging operation has stabilized; a refrigerant quantity calculating means configured to calculate a refrigerant quantity in the refrigerant circuit; and refrigerant quantity judging means configured to judge 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; characterized in that the air conditioner further comprises: condition changing means configured to change the target control value in the refrigerant quantity judging operation when it is judged that a refrigerant quantity judging operation has not stabilized; and that the stability judging means is configured to judge that the refrigerant quantity judging operation has not stabilized when a state in which a pressure of the refrigerant at a discharge side of the compressor or an operation state quantity equivalent to the pressure does not satisfy a predetermined high pressure condition or a state in which a pressure of the refrigerant at a suction side of the compressor or an operation state quantity equivalent to the pressure does not satisfy a predetermined low pressure condition continues for a predetermined period of time or longer. condition changing means configured to change the target control value in the refrigerant quantity judging operation when it is judged that a refrigerant quantity judging operation has not stabilized; and that the stability judging means is configured to judge that the refrigerant quantity judging operation has not stabilized when a state in which a pressure of the refrigerant at a discharge side of the compressor or an operation state quantity equivalent to the pressure does not satisfy a predetermined high pressure condition or a state in which a pressure of the refrigerant at a suction side of the compressor or an operation state quantity equivalent to the pressure does not satisfy a predetermined low pressure condition continues for a predetermined period of time or longer.