Provided is a heat exchanger which can suppress increase of pressure loss while improving nonuniform speed distribution of a fluid. In the heat exchanger (T), a fluid channel (4) is composed of flat containers (1, 2) having an inflow port (15) for the fluid at one end section and an outflow port (15) for the fluid at the other end section, and an offset type fin (5) arranged in the flat containers (1, 2). The heat exchanger is provided with a fin orthogonal intersection region (H) where the plate fin (5) orthogonally intersects with a flow direction of the fluid flowing from the inflow port (15) to the outflow port (16), and a fin parallel region (V) wherein the plate fin (5) is parallel to the flow direction of the fluid flowing from the inflow port (15) to the outflow port (16). The fin orthogonal intersection regions (H) are arranged on the sides of the inflow port (15) and the outflow port (16), and the fin parallel region (V) is arranged between the fin orthogonal intersection regions (H).