PURPOSE: To facilitate the manufacture of a heat exchanger having the laminated structure, by forming intermittent slits on a plate material and reaming these slits successively to form a band-shaped plate with through holes and cutting the band-shaped plate to combine them and fins alternately.

CONSTITUTION: Plate materials 12 are supplied between a roll 17 for primary slit, which has an edge for forming intermittent slits on the surface, and a plane-shaped roll 18. Then, primary intermittent and parallel slits 13 are formed on materials 12. When materials 12 are supplied between rolls 19 and 20 for seconddary slit, plural band-shaped plates 15 having primary slits 13 in the approximate center are formed. These slits 13 are reamed successively to prescribed through holes 16 by reaming rolls 21, 22, 23, and 24. Band-shaped materials 15 are cut properly to form spacers 6, and spacers 6 and fins 5 produced separately are combined and laminated to constitute a compact heat exchanger.