Abstract: A separate type heat exchanger characterized in that the evaporation section heated by the hot fluid is formed by fitting a plurality of the evaporation pipes horizontally between the vapor header pipe and the condensed liquid header pipe, the condensation section cooled by the cold fluid is formed above said evaporation section by fitting a plurality of the condensation pipes between the vapor header pipe and the condensed liquid header pipe, both vapor header pipes are connected through the vapor pipe and both condensed liquid header pipes are connected through the condensed liquid pipe to form a circulation path, and said path contains the working fluid is sealed within said path which circulates by evaporating at the evaporation section and condensing at the condensation section.