PURPOSE:To prevent leakage of heated fluid and improve heat exchanging rate per unit weight by a method wherein recesses and protrusions for engagement, which are provided on both surfaces of neighboring ceramic plates, are engaged and the tip end of a bulkhead is abutted against the recessed surface of the recess for engagement to form a plurality of heated fluid paths. CONSTITUTION:A ceramic plate 11 is provided with a plurality of recessed grooves 18 for forming a plurality of gas paths on the rectangular surface thereof from one side rim 14 to the other side rim 15 in parallel to both end faces 16, 17 and is divided by bulkheads 19. Air holes 20 penetrate through the ceramic plate 11 from one end face 16 to the other end face 17 orthogonally to said gas path forming recessed grooves 18 and is divided by bulkheads 22. The ceramic plates 11, 12, 13 may be connected air-tightly by engaging recesses 24 and protrusions 23 for engagement while a plurality of gas paths 26, having rectangular sections, are formed by abutting the tip end of the bulkheads 19 against the recessed surfaces 25 of the recesses 24 for engagement air-tightly. According to this method, the surface area per unit weight may be enlarged, the heat exchanging efficiency may be improved, air-tightness may be kept and the leakage of heated fluid may be prevented.