A heat exchanger comprising: a heat exchange unit in which heating medium flow channels through which a heating medium flows in a space between a plurality of plates and combustion gas flow channels through which a combustion gas combusted in a burner flows are alternately formed to be adjacent to each other, wherein the heat exchange unit is configured with a sensible heat unit configured to surround an outer side of a combustion chamber (C), configured with an area at one side of each one of the plates and configured to heat the heating medium using sensible heat of the combustion gas generated by combustion of the burner ; a latent heat unit configured with an area at the other side of each one of the plates and configured to heat the heating medium using latent heat of water vapor contained in the combustion gas which undergoes heat exchange in the sensible heat unit ; and a flange formed to be bent at an edge of each of the plurality of plates, and a plurality of combustion gas pass-through units (D) through which the combustion gas flowing in the combustion gas flow channel passes are formed at a part of an area of the edge of the plurality of plates in a state in which flanges of adjacent plates overlap characterised in that the combustion gas is distributed and discharged at a uniform flow rate across the entire lower area of the latent heat unit through the combustion gas pass-through units (D), wherein the combustion gas pass-through units (D) are formed and spaced a predetermined distance apart at the lower portion of the latent heat unit in horizontal and vertical directions. a heat exchange unit in which heating medium flow channels through which a heating medium flows in a space between a plurality of plates and combustion gas flow channels through which a combustion gas combusted in a burner flows are alternately formed to be adjacent to each other, wherein the heat exchange unit is configured with a sensible heat unit configured to surround an outer side of a combustion chamber (C), configured with an area at one side of each one of the plates and configured to heat the heating medium using sensible heat of the combustion gas generated by combustion of the burner ; a latent heat unit configured with an area at the other side of each one of the plates and configured to heat the heating medium using latent heat of water vapor contained in the combustion gas which undergoes heat exchange in the sensible heat unit ; and a flange formed to be bent at an edge of each of the plurality of plates, and a plurality of combustion gas pass-through units (D) through which the combustion gas flowing in the combustion gas flow channel passes are formed at a part of an area of the edge of the plurality of plates in a state in which flanges of adjacent plates overlap characterised in that the combustion gas is distributed and discharged at a uniform flow rate across the entire lower area of the latent heat unit through the combustion gas pass-through units (D), wherein the combustion gas pass-through units (D) are formed and spaced a predetermined distance apart at the lower portion of the latent heat unit in horizontal and vertical directions. <EOS>