A multi-air conditioner for heating and cooling operations comprising: at least one indoor unit for both cooling and heating comprising an indoor heat exchanger; an outdoor unit for both cooling and heating comprising a compressor (53, 54), a plurality of outdoor heat exchangers (A1 to A3), and a switching unit disposed on a discharge side of the compressor to switch the flow of a refrigerant; and a distributor disposed between the outdoor unit for both cooling and heating and the at least one indoor unit for both cooling and heating, for distributing the refrigerant, wherein the plurality of outdoor heat exchangers (A1 to A3) in the outdoor unit for both cooling and heating comprises: a first heat exchanger, one end of which is connected to the switching unit, and the other end of which is connected to the distributor; a second heat exchanger disposed under the first heat exchanger, one end of which is couplable to or decouplable from the other end of the first heat exchanger, and the other end of which is connected to the distributor; a third heat exchanger disposed under the second heat exchanger, one end of which is connected to the discharge side of the compressor (53, 54), and the other end of which is connected to the indoor unit, wherein the outdoor unit for both cooling and heating further comprises: a connecting pipeline connecting the end of the first heat exchanger and the one end of the second heat exchanger in series; and a first connecting valve disposed on the connecting pipeline, for switching on or off a mechanical connection between the first heat exchanger and the second heat exchanger, and wherein the first heat exchanger has a longer flow path than the second heat exchanger, and the third heat exchanger has a shorter flow path than the second heat exchanger. at least one indoor unit for both cooling and heating comprising an indoor heat exchanger; an outdoor unit for both cooling and heating comprising a compressor (53, 54), a plurality of outdoor heat exchangers (A1 to A3), and a switching unit disposed on a discharge side of the compressor to switch the flow of a refrigerant; and a distributor disposed between the outdoor unit for both cooling and heating and the at least one indoor unit for both cooling and heating, for distributing the refrigerant, wherein the plurality of outdoor heat exchangers (A1 to A3) in the outdoor unit for both cooling and heating comprises: a first heat exchanger, one end of which is connected to the switching unit, and the other end of which is connected to the distributor; a second heat exchanger disposed under the first heat exchanger, one end of which is couplable to or decouplable from the other end of the first heat exchanger, and the other end of which is connected to the distributor; a third heat exchanger disposed under the second heat exchanger, one end of which is connected to the discharge side of the compressor (53, 54), and the other end of which is connected to the indoor unit, a first heat exchanger, one end of which is connected to the switching unit, and the other end of which is connected to the distributor; a second heat exchanger disposed under the first heat exchanger, one end of which is couplable to or decouplable from the other end of the first heat exchanger, and the other end of which is connected to the distributor; a third heat exchanger disposed under the second heat exchanger, one end of which is connected to the discharge side of the compressor (53, 54), and the other end of which is connected to the indoor unit, wherein the outdoor unit for both cooling and heating further comprises: a connecting pipeline connecting the end of the first heat exchanger and the one end of the second heat exchanger in series; and a first connecting valve disposed on the connecting pipeline, for switching on or off a mechanical connection between the first heat exchanger and the second heat exchanger, and a connecting pipeline connecting the end of the first heat exchanger and the one end of the second heat exchanger in series; and a first connecting valve disposed on the connecting pipeline, for switching on or off a mechanical connection between the first heat exchanger and the second heat exchanger, and wherein the first heat exchanger has a longer flow path than the second heat exchanger, and the third heat exchanger has a shorter flow path than the second heat exchanger.