A heat exchanger, comprising: a heat exchanging body , comprising at least three layers of flat tubes , wherein each layer of at least three layers of flat tubes comprises a plurality of micro-channels , and the at least three layers of flat tubes are laminated on each other; and a fluid-collecting tube assembly , comprising a first fluid-collecting tube and a second fluid-collecting tube , wherein ends of some of the at least three layers of flat tubes are connected to the first fluid-collecting tube ; the at least three layers of flat tubes comprise flat tubes that are disposed at an outer side of the at least three layers of flat tubes ; and ends of the flat tubes that are disposed at an outer side of the at least three layers of flat tubes avoid the first fluid-collecting tube and are connected to the second fluid-collecting tube , wherein the at least three layers of flat tubes comprise two layers of first flat tubes ; ends of the two layers of first flat tubes are connected to the first fluid-collecting tube ; and two layers of the second flat tubes are disposed at the outer side of the at least three layers of flat tubes , and ends of the two layers of second flat tubes are bent to avoid the first fluid-collecting tube to be connected to the second fluid-collecting tube , characterized in that the at least three layers of flat tubes comprise three layers of second flat tubes , one layer of the three layers of second flat tubes are disposed between the two layers of first flat tubes , and ends of the one layer of second flat tubes extend through the first fluid-collecting tube and is connected to the second fluid-collecting tube . a heat exchanging body , comprising at least three layers of flat tubes , wherein each layer of at least three layers of flat tubes comprises a plurality of micro-channels , and the at least three layers of flat tubes are laminated on each other; and a fluid-collecting tube assembly , comprising a first fluid-collecting tube and a second fluid-collecting tube , wherein ends of some of the at least three layers of flat tubes are connected to the first fluid-collecting tube ; the at least three layers of flat tubes comprise flat tubes that are disposed at an outer side of the at least three layers of flat tubes ; and ends of the flat tubes that are disposed at an outer side of the at least three layers of flat tubes avoid the first fluid-collecting tube and are connected to the second fluid-collecting tube , wherein the at least three layers of flat tubes comprise two layers of first flat tubes ; ends of the two layers of first flat tubes are connected to the first fluid-collecting tube ; and two layers of the second flat tubes are disposed at the outer side of the at least three layers of flat tubes , and ends of the two layers of second flat tubes are bent to avoid the first fluid-collecting tube to be connected to the second fluid-collecting tube , characterized in that the at least three layers of flat tubes comprise three layers of second flat tubes , one layer of the three layers of second flat tubes are disposed between the two layers of first flat tubes , and ends of the one layer of second flat tubes extend through the first fluid-collecting tube and is connected to the second fluid-collecting tube . <EOS>