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.