A round plate heat exchanger of the present invention has a heat exchange part in which heat medium flow paths and combustion gas flow paths are formed so as to be alternatingly adjacent to each other in a space among a plurality of plates, wherein the plurality of plates forming the heat exchange part are formed by stacking a plurality of unit plates comprising a first plate and a second plate stacked therein, the plurality of heat medium flow paths are formed to be spaced from each other between the first plate and the second plate of the unit plate, a heat medium connection flow path is formed in a part of the region of the heat medium flow paths located adjacent to each other, and the combustion gas flow path is formed between the second plate of the unit plate, located at one side of the unit plate, among the unit plates, which are stacked adjacent to each other, and the first plate of the unit plate, located at the other side of the unit plate.