Heat exchanger

A body (6) of a heat exchanger is provided with a plurality of heat receiving fluid passages (10A) having openings directed upward. A header (1) is fitted to the top of the body (6). The header (1) has a bottom plate (1B) having a plurality of through holes (4) communicating with the openings of the passages (10A), a top plate (1A) fixed to the bottom plate (1B). In the header (1), a plurality of fluid passages (5) communicating with the through holes (4) and a fuel distribution space (8) communicating with the fluid conducting passages (5) are partitioned. By supplying heat receiving fluid from a fuel supply member (3) fixed to a lateral face of the header (1) to the fuel distribution space (8), the heat receiving fluid is supplied to the heat receiving fluid passages (10A) quickly and uniformly.