PURPOSE: A heat exchanger is provided to improve the durability and corrosion-resistance of the heat exchanger and to improve welding strength. CONSTITUTION: A heat exchanger comprises multiple tubes(110) and tube fixing plates(120). Hot water passes through the inside the tubes. The tubes are installed to be parallel to each other. The tube fixing plates are coupled to both ends of the tubes and fix the tubes at uniform intervals. Multiple slot type fixing holes(130) are formed in the tube fixing plates. The fixing holes correspond to the shape of the tubes. Protrusions(125) are formed in the edges of the fixing holes. The outer surfaces of the protrusions are contact with the inner sides of the tubes. The ends of the tubes are contact with the flat parts of the tube fixing plates.
