A condensing-type heat exchanger with high efficiency is composed of a tubular shell (8), an upper water tank (3), upper spiral casing pipes (6), a middle water tank (10), lower spiral casing pipes (13), a lower water tank (16) and a U-shaped condensate-collecting fume extractor (19). Thermal energy generated in combustion is absorbed by water in the heat exchanger, the temperature of fume decreasing, vapor in the fume being condensed and latent heat released in the condensation process being absorbed, thereby heat exchange efficiency can be improved.
