PURPOSE: To form the exhaust gas heat exchanger, having high efficiency, generating low noise and integral with a muffler, by constituting an exhaust gas space with a special constitution.

CONSTITUTION: The internal exhaust gas space 5, enclosed by the water chamber 4 of the heat exchanger, is partitioned by a plurality of partitioning plates 6 and double tubes, whose inside is heat transfer tubes 12 and whose outside is exhaust gas tubes 13, are penetrating through the partitioning plates 6. A plurality of holes 14 are provided on the exhaust gas tube 13, opened in the different exhaust gas spaces 5, and a non-return valve 15 is provided on the inner wall of the exhaust gas tube 13 at the downstream area of the hole 14. Exhaust gas from an engine or the like enters into the space 5 through an introducing tube 16, passes through the tube 13 and is discharged from a discharging tube 17. In this case, heat exchage is effected effectively by colliding the exhaust gas against the inside surface of the water chamber 4 or the heat transfer tube 12 directly or passing the exhaust gas through the double tube. When the exchaust gas (a) enters into the tube 13, the flow thereof is contracted suddenly and the expansion type muffler is formed and, further, the space 5 are divided into a plurality of spaces, therefore, a multi-stage expansion type muffler effect may be obtained.