An air conditioner that constitutes a closed-cycle refrigerant circuit in which an outdoor unit including a compressor, an outdoor heat exchanger, a heating expansion valve, a receiver that stores a liquid refrigerant, and a supercooling circuit that, after diverting a flow of one part of a liquid refrigerant and decompressing the refrigerant by means of a decompression mechanism, causes the refrigerant to exchange heat with a liquid refrigerant at a supercooling heat exchanger and returns the refrigerant to an intake side of the compressor and the like, and an indoor unit that includes an indoor heat exchanger and a cooling expansion valve and the like are connected by gas refrigerant piping and liquid refrigerant piping; the air conditioner comprising: a first refrigerant liquid level detecting circuit in which an on/off valve and a decompression mechanism are interposed in a bypass circuit that connects a predetermined height position of the receiver and an intake side of the compressor via the supercooling circuit; a second refrigerant liquid level detecting circuit that is branched from the bypass circuit and in which an on/off valve is interposed that acts as a bypass for leading a refrigerant that is taken out from the receiver to an inlet side of a decompression mechanism of the supercooling circuit; a temperature detecting unit that detects a temperature of decompressed refrigerant that passes through the supercooling circuit including the first refrigerant liquid level detecting circuit or the second refrigerant liquid level detecting circuit; and a refrigerant amount detecting unit that detects, by means of the temperature detecting unit, a temperature after decompression of a refrigerant that is taken out from the receiver via the first refrigerant liquid level detecting circuit or the second refrigerant liquid level detecting circuit, and determines a refrigerant filling amount based on the temperature, characterized in that the refrigerant amount detecting unit performs refrigerant liquid-level detection under a temperature condition of a cooling rating extent by closing the second refrigerant liquid level detecting circuit by means of the on/off valve, and performs a refrigerant liquid-level detection under a condition of a low outside air temperature by using the second refrigerant liquid level detecting circuit. a first refrigerant liquid level detecting circuit in which an on/off valve and a decompression mechanism are interposed in a bypass circuit that connects a predetermined height position of the receiver and an intake side of the compressor via the supercooling circuit; a second refrigerant liquid level detecting circuit that is branched from the bypass circuit and in which an on/off valve is interposed that acts as a bypass for leading a refrigerant that is taken out from the receiver to an inlet side of a decompression mechanism of the supercooling circuit; a temperature detecting unit that detects a temperature of decompressed refrigerant that passes through the supercooling circuit including the first refrigerant liquid level detecting circuit or the second refrigerant liquid level detecting circuit; and a refrigerant amount detecting unit that detects, by means of the temperature detecting unit, a temperature after decompression of a refrigerant that is taken out from the receiver via the first refrigerant liquid level detecting circuit or the second refrigerant liquid level detecting circuit, and determines a refrigerant filling amount based on the temperature, characterized in that the refrigerant amount detecting unit performs refrigerant liquid-level detection under a temperature condition of a cooling rating extent by closing the second refrigerant liquid level detecting circuit by means of the on/off valve, and performs a refrigerant liquid-level detection under a condition of a low outside air temperature by using the second refrigerant liquid level detecting circuit.