Abstract: A heat exchanger comprises a tube 11 and fin plates 12 attached to the outer surface of the tube. Each fin plate 12 is in the form of a strip sheet which is wider than the diameter of the tube 11, and each fin plate 12 is fitted on the tube 11 and has a semicylindrical recess 20 in the form corresponding to the cylindrical shape of the tube 11. Flat fins 21 extend from both sides of the semicylindrical recess 20. Cut pieces 22a are formed each by a U-shaped cut 22 at a predetermined pitch in the longitudinal direction of the semicylindrical recess 20, and each cut piece is erected outwardly of the semicylindrical recess to thereby form an upstanding fin 23, which is formed on a first fin plate element 18 as well as a second fin plate element 19. Straight tube portion 15 of the tube 11 is fitted between the semicylindrical recesses 20 of the first fin plate element 18 and the second fin plate element 19. In this way, the tube and the fin plate 12 are secured.