An air conditioning device which includes: a refrigerant circuit including an outdoor unit and indoor units connected to each other via an interconnecting pipe (71,72); and an operation controller controlling operation of the refrigerant circuit, the interconnecting pipe (71,72) including: a liquid main pipe connected to the outdoor unit, and liquid branch pipes branching off from the liquid main pipe and each connected to a corresponding one of the indoor units; and a gas main pipe connected to the outdoor unit, and gas branch pipes branching off from the gas main pipe and each connected to a corresponding one of the indoor units, the operation controller including an oil collection controller calculating, at predetermined time intervals, an amount of refrigerating machine oil accumulated in the interconnecting pipe (71,72) during the operation, and integrating the amount calculated for each predetermined time interval, and when a value of the integration exceeds a set amount, performing oil collecting operation for collecting the refrigerating machine oil in the refrigerant circuit into the compressor, wherein the oil collection controller includes an oil accumulation amount calculator (i) determining that, when a flow rate of a gaseous refrigerant in the gas main pipe is determined to be lower than a preset lower limit flow rate in main pipe, the refrigerating machine oil is accumulated in the gas main pipe, and calculating an amount of the refrigerating machine oil accumulated in the gas main pipe as an amount of oil accumulated in main pipe, characterised by: the oil accumulation amount calculator further (ii) determining that, when the flow rate of the gaseous refrigerant in the gas main pipe is determined to be higher than the preset lower limit flow rate in main pipe and the gas branch pipes are determined to include a gas branch pipe having a flow rate of the gaseous refrigerant higher than a preset lower limit flow rate in branch pipe and a gas branch pipe having a flow rate of the gaseous refrigerant lower than the preset lower limit flow rate in branch pipe, the refrigerating machine oil is accumulated in the gas branch pipe having the flow rate of the gaseous refrigerant lower than the preset set lower limit flow rate in branch pipe, and calculating an amount of the refrigerating machine oil accumulated in the gas branch pipe as an amount of oil accumulated in branch pipe, the oil accumulation amount calculator calculating the integrated value from the amount of oil accumulated in main pipe and the amount of oil accumulated in branch pipe. a refrigerant circuit including an outdoor unit and indoor units connected to each other via an interconnecting pipe (71,72); and an operation controller controlling operation of the refrigerant circuit, the interconnecting pipe (71,72) including: a liquid main pipe connected to the outdoor unit, and liquid branch pipes branching off from the liquid main pipe and each connected to a corresponding one of the indoor units; and a gas main pipe connected to the outdoor unit, and gas branch pipes branching off from the gas main pipe and each connected to a corresponding one of the indoor units, the operation controller including an oil collection controller calculating, at predetermined time intervals, an amount of refrigerating machine oil accumulated in the interconnecting pipe (71,72) during the operation, and integrating the amount calculated for each predetermined time interval, and when a value of the integration exceeds a set amount, performing oil collecting operation for collecting the refrigerating machine oil in the refrigerant circuit into the compressor, wherein the oil collection controller includes an oil accumulation amount calculator (i) determining that, when a flow rate of a gaseous refrigerant in the gas main pipe is determined to be lower than a preset lower limit flow rate in main pipe, the refrigerating machine oil is accumulated in the gas main pipe, and calculating an amount of the refrigerating machine oil accumulated in the gas main pipe as an amount of oil accumulated in main pipe, characterised by: the oil accumulation amount calculator further (ii) determining that, when the flow rate of the gaseous refrigerant in the gas main pipe is determined to be higher than the preset lower limit flow rate in main pipe and the gas branch pipes are determined to include a gas branch pipe having a flow rate of the gaseous refrigerant higher than a preset lower limit flow rate in branch pipe and a gas branch pipe having a flow rate of the gaseous refrigerant lower than the preset lower limit flow rate in branch pipe, the refrigerating machine oil is accumulated in the gas branch pipe having the flow rate of the gaseous refrigerant lower than the preset set lower limit flow rate in branch pipe, and calculating an amount of the refrigerating machine oil accumulated in the gas branch pipe as an amount of oil accumulated in branch pipe, the oil accumulation amount calculator calculating the integrated value from the amount of oil accumulated in main pipe and the amount of oil accumulated in branch pipe.