PURPOSE: To reinforce an inner ceramic pipe and to increase the allowable amount of offset in axial direction by providing an annular collar that projects toward the inside in radius direction while being engaged between edge parts at a sleeve that coaxially surrounds the edge part of pipe part pieces that needy to be connected each other.

CONSTITUTION: A number of pipe part pieces 6 for forming an inner ceramic pipe 5 are connected by a sleeve 8 for surrounding axially. An annular collar 9 that projects toward the inside in radius direction and is engaged between the adjacent edge parts of the pipe part pieces 6 is carried in the middle of the longer direction on the inner surface in radius direction of the sleeve 8. The inner diameter of the collar 9 is essentially equivalent to the inner diameter of the pipe part pieces 6, its outer diameter is slightly larger than the outer diameter of the pipe part pieces 6, and a certain degree of play in radius direction is given by considering an offset in the axial direction of the pipe part pieces 6 while airtightness and liquid-tight sealing are secured at a pipe part piece interlocking part. The diameter of an inner surface part 10 located at both edges of the collar 9 gradually increases toward the edge part of the sleeve 8.