It is an object of the present invention to obtain a compact and high performance heat exchanger low in its pressure loss of fluid and a refrigerating air conditioner. The heat exchanger of the present invention is a heat exchanger 10 including a first flat tube 1 in which a low temperature fluid flows and a second flat tube 2 in which a high temperature fluid flows that is laminated on the first flat tube and arranged so that the flowing direction of the high temperature fluid is parallel to the flowing direction of the low temperature fluid. At least one of the flat tubes is formed with a plurality of flat tubes arranged in the direction of lamination. Both ends of the plurality of the flat tubes are bent in the direction intersecting at right angles to both the flowing directions of the fluids respectively and the direction of lamination. Parallel passages are formed by the plurality of the flat tubes and an inlet header and an outlet header. Either of the inlet header or the outlet header is formed with a tubular header. The plurality of the flat tubes forming the parallel passages are bundled and connected to the tubular header so that the axial direction of the tubular header is the same as the flowing direction of the fluid in the flat tube.
