PURPOSE: To obtain the horizontal type multi-tube system gas-to-gas heat exchanger, long in life and capable of showing merits in the resistances to heat and corrosion of ceramics, by a method wherein the heat exchanger is provided with a structure without possibility of breakage even if a thin slender ceramic tube is utilized.

CONSTITUTION: An outlet side header 4 or the outlet side header 4 and an inlet side header 3 are separated from a structure 1 and are hung by a wire 6 while the wire 6 is extended from a pulley 7 and a counter-weight 8, balancing with the weights of the headers 3, 4, is attached to the end of the wire at the opposite side of the headers. Air-tight between the structure 1 and the headers 3, 4 is kept under permitting the sliding of the headers 3, 4. The headers 3, 4 and a conduit for gas to be heated are connected through flexible tubes 22A, 22B. The headers 3, 4 are being hung under a balance with the counter-weight 8, therefore, the headers 3, 4 move to positions which imparts no stress to the ceramic tube 2 when deformation or the like is caused in the structure 1.