PURPOSE: To lessen the collapse of a granular reforming catalyst caused by the thermal deformation of a reforming pipe by using plural connected members each composed of reforming catalysts connected with each other by a string and keeping the catalysts in a state mutually separated by the string.

CONSTITUTION: A through-hole having the smallest possible diameter to allow the passage of a string 38 is opened on each granular reforming catalyst 39 to be filled in a catalyst layer 3 to obtain a connected member 31 having a number of catalyst granules 39 connected with each other in the form of a rosary. The connected member 31 is held with the string 38 by a holding means placed at the lower face 21a of an upper plate 21. The connected members 31 adjacent to each other in the circumferential direction of the inner ring- shaped space 86 are arranged in such a manner as to contact the outer circumferences of the catalyst granules 39 with each other. The gap L between the adjacent connected members 31 is made to be larger than the average gap LS of the reforming catalyst defined by the outer diameter D of the granular catalyst 39 by about 10%. There is no application of a pressing force to the granular catalyst 39 caused by the deformation of the inner pipe 82 by this structure to prevent the collapse of the granular catalyst 39.