The present invention relates to an integrated heat exchanger in which a flow path, in which a first heat exchange medium flows, and a flow path, in which a second heat exchange medium flows, are separated by means of a baffle. The integrated heat exchanger of the present invention has: a support surface having a slope of which the height lowers toward the outside, and formed at a header portion coming in contact with a gasket baffle sealing part, and the gasket baffle sealing part formed in a shape corresponding to the support surface of a header such that the deformation of a gasket can be prevented when a tank and the header of a header tank are coupled, and a problem in which the gasket of a coupling part, at which the baffle is positioned, is non-uniformly compressed or the gasket is broken or separated from a designated position by means of force of the other direction is prevented, and thus the sealing performance of the header tank can be more improved.