An air conditioner comprising: an outdoor unit; a plurality of indoor units (5a to 5c) respectively including indoor heat exchangers (51a to 51c); expansion valves (52a to 52c) respectively provided to the plurality of indoor units (5a to 5c), the expansion valves (52a to 52c) being configured to adjust flow rates of a refrigerant in the indoor heat exchangers (51a to 51c); and a controller (210, 510a, 510b and/or 510c) for executing a refrigerant amount balance control configured to adjust opening degrees of the expansion valves (52a to 52c) so that operation state amounts (SH, SC), with which the indoor heat exchangers (51a to 51c) exert heat exchange amounts, of the plurality of indoor units (5a to 5c) become equal to each other, wherein the operation state amounts (SH, SC) are refrigerant superheating degrees in refrigerant exit openings of the indoor heat exchangers (51a to 51c) during a cooling operation, wherein the controller (210, 510a, 510b and/or 510c) calculates an average value (SHv) of the refrigerant superheating degrees from a maximum value and a minimum value of the refrigerant superheating degrees of the plurality of indoor units (5a to 5c), and adjusts the opening degrees of the expansion valves (52a to 52c) so that the refrigerant superheating degrees of the plurality of indoor units (5a to 5c) reach the average value (SHv), wherein the operation state amounts (SH, SC) are refrigerant subcooling degrees in refrigerant exit openings of the indoor heat exchangers (51a to 51c) during a heating operation, and wherein the controller (210, 510a, 510b and/or 510c) calculates an average value (SCv) of the refrigerant subcooling degrees from a maximum value and a minimum value of the refrigerant subcooling degrees of the plurality of indoor units (5a to 5c), and adjusts the opening degrees of the expansion valves (52a to 52c) so that the refrigerant subcooling degrees of the plurality of indoor units (5a to 5c) reach the average value (SCv). an outdoor unit; a plurality of indoor units (5a to 5c) respectively including indoor heat exchangers (51a to 51c); expansion valves (52a to 52c) respectively provided to the plurality of indoor units (5a to 5c), the expansion valves (52a to 52c) being configured to adjust flow rates of a refrigerant in the indoor heat exchangers (51a to 51c); and a controller (210, 510a, 510b and/or 510c) for executing a refrigerant amount balance control configured to adjust opening degrees of the expansion valves (52a to 52c) so that operation state amounts (SH, SC), with which the indoor heat exchangers (51a to 51c) exert heat exchange amounts, of the plurality of indoor units (5a to 5c) become equal to each other, wherein the operation state amounts (SH, SC) are refrigerant superheating degrees in refrigerant exit openings of the indoor heat exchangers (51a to 51c) during a cooling operation, wherein the controller (210, 510a, 510b and/or 510c) calculates an average value (SHv) of the refrigerant superheating degrees from a maximum value and a minimum value of the refrigerant superheating degrees of the plurality of indoor units (5a to 5c), and adjusts the opening degrees of the expansion valves (52a to 52c) so that the refrigerant superheating degrees of the plurality of indoor units (5a to 5c) reach the average value (SHv), wherein the operation state amounts (SH, SC) are refrigerant subcooling degrees in refrigerant exit openings of the indoor heat exchangers (51a to 51c) during a heating operation, and wherein the controller (210, 510a, 510b and/or 510c) calculates an average value (SCv) of the refrigerant subcooling degrees from a maximum value and a minimum value of the refrigerant subcooling degrees of the plurality of indoor units (5a to 5c), and adjusts the opening degrees of the expansion valves (52a to 52c) so that the refrigerant subcooling degrees of the plurality of indoor units (5a to 5c) reach the average value (SCv).