PURPOSE: To absorb the counterforce of thermal expansion by a method wherein, in the title boiler being composed of a plurality of modules, between the modules adjoining each other at one of them and a support stand, a fixed fulcrum and a sliding plate are arranged facing each other, while another module is equipped with a plurality of sliding plates and the above-mentioned support stands, and the two support stands are connected with a connecting member.

CONSTITUTION: Thermal expansion difference between a support stand 21A and a module A is absorbed in the manner that the module A is supported by a support stand 21A, while the center fulcrum and both fulcrums are interposed with the sliding plates 22. The module B functions that while being supported by the support stand 21B, and also by the aid of a fixing member 23B being provided at the side A, which is void of fixing fulcrum, to act as a fixing fulcrum for the thermal expansion of the module, said module B connects with the module A by welding. At its opposite side, a sliding plate 22 is arranged, while both supporting stands 21A and 21B are connected by a connecting member 24. The module C, D are structured in a similar manner sequentially. By this constitution, the thermal expansion counterforce can be absorbed.