A method for controlling an air conditioning apparatus comprising steps of: circulating a refrigerant between an outdoor unit and a plurality of indoor units via a refrigerant pipe , the plurality of indoor units including at least one non-operating indoor unit that is not in operation and at least one operating indoor unit that is in operation; acquiring an operating state of each of the plurality of indoor units ; determining whether oil level of a compressor of the outdoor unit is decreased or not; and determining, when the oil level of the compressor is determined to be decreased, whether (a) an oil recovery operation is performed by opening an expansion valve corresponding to only the at least one operating-indoor unit or (b) an oil recovery operation is performed by opening expansion valves corresponding to all of the plurality of indoor units , characterised in that the method further comprises the steps of determining whether an operating rate of the indoor units is equal to or higher than a threshold, when the oil level of the compressor determined to be decreased, wherein the operating rate is a ratio of a total capacity of the at least one operating indoor unit to a total capacity of all of the plurality of indoor units connected to the outdoor unit via the refrigerant pipe ; performing the oil recovery operation by opening the expansion valve corresponding to only the at least one operating indoor unit , when the operating rate of the plurality of indoor units is determined to be equal to or higher than the threshold; and performing the oil recovery operation by opening the expansion valves corresponding to all of the plurality of indoor units , when the operating rate of the plurality of indoor units is determined to be lower than the threshold. circulating a refrigerant between an outdoor unit and a plurality of indoor units via a refrigerant pipe , the plurality of indoor units including at least one non-operating indoor unit that is not in operation and at least one operating indoor unit that is in operation; acquiring an operating state of each of the plurality of indoor units ; determining whether oil level of a compressor of the outdoor unit is decreased or not; and determining, when the oil level of the compressor is determined to be decreased, whether (a) an oil recovery operation is performed by opening an expansion valve corresponding to only the at least one operating-indoor unit or (b) an oil recovery operation is performed by opening expansion valves corresponding to all of the plurality of indoor units , characterised in that the method further comprises the steps of determining whether an operating rate of the indoor units is equal to or higher than a threshold, when the oil level of the compressor determined to be decreased, wherein the operating rate is a ratio of a total capacity of the at least one operating indoor unit to a total capacity of all of the plurality of indoor units connected to the outdoor unit via the refrigerant pipe ; performing the oil recovery operation by opening the expansion valve corresponding to only the at least one operating indoor unit , when the operating rate of the plurality of indoor units is determined to be equal to or higher than the threshold; and performing the oil recovery operation by opening the expansion valves corresponding to all of the plurality of indoor units , when the operating rate of the plurality of indoor units is determined to be lower than the threshold. <EOS>