A heat exchanger comprising: a plurality of heat exchanging bodies including a first heat exchanging body and a second heat exchanging body, the first and second heat exchanging bodies each including a first heat exchanging portion including first and second flat tubes (P1, P2) stacked in parallel with each other to allow fluid to pass between the first and second flat tubes (P1, P2); and a second heat exchanging portion including third and fourth flat tubes (P3, P4) stacked in parallel with each other to allow fluid to pass between the third and fourth flat tubes (P3, P4), the second heat exchanging body being arranged downstream of the first heat exchanging body in a direction of the flow of the fluid, the first heat exchanging body and the second heat exchanging body being configured such that the third flat tube of the second heat exchanging portion is oriented crosswise to the first flat tube of the first heat exchanging portion in a cross-section perpendicular to a longitudinal direction of the third flat tube, the fourth flat tube of the second heat exchanging portion is oriented crosswise to the second flat tube of the first heat exchanging portion in a cross-section perpendicular to a longitudinal direction of the fourth flat tube, the heat exchanger being characterized in that the lengths of the first and second flat tubes (P1, P2) of the second heat exchanging body in a transverse direction are larger than lengths of the first and second flat tubes (P1, P2) of the first heat exchanging body in the transverse direction, in that angles formed between the first and second flat tubes (P1, P2) of the second heat exchanging body and the direction of the flow of the fluid are smaller than angles formed between the first and second flat tubes (P1, P2) of the first heat exchanging body and the direction of the flow of the fluid, in that lengths of the third and fourth flat tubes (P3, P4) of the second heat exchanging body in the transverse direction are larger than lengths of the third and fourth flat tubes (P3, P4) of the first heat exchanging body in the transverse direction, and in that angles formed between the third and fourth flat tubes (P3, P4) of the second heat exchanging body and the direction of the flow of the fluid are smaller than angles formed between the third and fourth flat tubes (P3, P4) of the first heat exchanging body and the direction of the flow of the fluid. a plurality of heat exchanging bodies including a first heat exchanging body and a second heat exchanging body, the first and second heat exchanging bodies each including a first heat exchanging portion including first and second flat tubes (P1, P2) stacked in parallel with each other to allow fluid to pass between the first and second flat tubes (P1, P2); and a second heat exchanging portion including third and fourth flat tubes (P3, P4) stacked in parallel with each other to allow fluid to pass between the third and fourth flat tubes (P3, P4), the second heat exchanging body being arranged downstream of the first heat exchanging body in a direction of the flow of the fluid, the first heat exchanging body and the second heat exchanging body being configured such that the third flat tube of the second heat exchanging portion is oriented crosswise to the first flat tube of the first heat exchanging portion in a cross-section perpendicular to a longitudinal direction of the third flat tube, the fourth flat tube of the second heat exchanging portion is oriented crosswise to the second flat tube of the first heat exchanging portion in a cross-section perpendicular to a longitudinal direction of the fourth flat tube, the heat exchanger being characterized in that the lengths of the first and second flat tubes (P1, P2) of the second heat exchanging body in a transverse direction are larger than lengths of the first and second flat tubes (P1, P2) of the first heat exchanging body in the transverse direction, in that angles formed between the first and second flat tubes (P1, P2) of the second heat exchanging body and the direction of the flow of the fluid are smaller than angles formed between the first and second flat tubes (P1, P2) of the first heat exchanging body and the direction of the flow of the fluid, in that lengths of the third and fourth flat tubes (P3, P4) of the second heat exchanging body in the transverse direction are larger than lengths of the third and fourth flat tubes (P3, P4) of the first heat exchanging body in the transverse direction, and in that angles formed between the third and fourth flat tubes (P3, P4) of the second heat exchanging body and the direction of the flow of the fluid are smaller than angles formed between the third and fourth flat tubes (P3, P4) of the first heat exchanging body and the direction of the flow of the fluid.