An air conditioning system performing a refrigeration cycle in a refrigerant circuit including an outdoor unit, a plurality of indoor units, a refrigerant connection pipe (GC, LC) connecting the outdoor unit and the indoor units, the air conditioning system comprising: electric valves (16, 17, 41) configured to decompress a refrigerant flowing in the refrigerant circuit in accordance with an opening degree; a detection portion (70, 74) configured to detect change of the number of operating units that are the indoor units under operation; and a control portion (70, 75) configured to control a state of the electric valves, the electric valves include a first electric valve (16, 17) and a second electric valve, the first electric valve (16, 17) is configured to decompress the refrigerant such that the refrigerant flowing from the outdoor unit to the indoor units passes through the refrigerant connection pipe in the gas-liquid two-phase state, the second electric valve is configured to decompress the refrigerant that flows from the refrigerant connection pipe to the corresponding indoor unit, and the control portion (70, 75) is configured to adjust a decompression ratio of the first electric valve (16, 17) such that the pressure of the refrigerant flowing into the second electric valve is suppressed from rising temporarily in the first control, characterized in that the air conditioning system further comprises a storage portion configured to store capacity information that specifies an air conditioning capacity of each of the indoor units; wherein the control portion is configured to execute a first control when the change of the number of operating units is detected by the detection portion, and when the change of the number of operating units is detected by the detection portion, the control portion is configured to execute the first control on condition of the system being in a first state in which a total value of the air conditioning capacities of the indoor units having been subject to change of an operating state is a predetermined reference value or more, and in that the reference value is a value at which an occurrence of variation in an operating capacity of the system is estimated at a level that causes an increase of noise in the operating unit. electric valves (16, 17, 41) configured to decompress a refrigerant flowing in the refrigerant circuit in accordance with an opening degree; a detection portion (70, 74) configured to detect change of the number of operating units that are the indoor units under operation; and a control portion (70, 75) configured to control a state of the electric valves, the electric valves include a first electric valve (16, 17) and a second electric valve, the first electric valve (16, 17) is configured to decompress the refrigerant such that the refrigerant flowing from the outdoor unit to the indoor units passes through the refrigerant connection pipe in the gas-liquid two-phase state, the second electric valve is configured to decompress the refrigerant that flows from the refrigerant connection pipe to the corresponding indoor unit, and the control portion (70, 75) is configured to adjust a decompression ratio of the first electric valve (16, 17) such that the pressure of the refrigerant flowing into the second electric valve is suppressed from rising temporarily in the first control, characterized in that the air conditioning system further comprises a storage portion configured to store capacity information that specifies an air conditioning capacity of each of the indoor units; wherein the control portion is configured to execute a first control when the change of the number of operating units is detected by the detection portion, and when the change of the number of operating units is detected by the detection portion, the control portion is configured to execute the first control on condition of the system being in a first state in which a total value of the air conditioning capacities of the indoor units having been subject to change of an operating state is a predetermined reference value or more, and in that the reference value is a value at which an occurrence of variation in an operating capacity of the system is estimated at a level that causes an increase of noise in the operating unit.