PURPOSE: To make possible tight adhesion without generating a gap between both peripheral areas by energizing an electric thermal element and fusing the inner peripheral face of a tubular coupling to the outer peripheral face of a thermoplastic resin tube after fixing the tubular coupling to the thermoplastic resin tube using a fixing bracket on the outer side of the tubular coupling.

CONSTITUTION: The end part of a thermoplastic resin tube of polyethylene is introduced into the socket 21, of a tubular coupling, which is provided on both end parts and contains an electrothermal element 22 embedded in the inner peripheral face of the socket 21. In addition, the electrothermal element 22 embedded in the inner peripheral face of the socket is energized to fuse the inner peripheral face of the tubular coupling to the outer peripheral face of the tube. Further, the tubular coupling 2 is fixed to the thermoplastic resin tube 1 using a fixing bracket A provided near an area outside the tubular coupling 2. After that, the electrothermal element 22 is energized to fuse the inner peripheral face of the tubular coupling 2 to the outer peripheral face of the thermoplastic resin tube 1. Further, the fixing bracket A is composed of a ring 4 and a rubber annulus 5, and is fixed by pressing the outer peripheral face of the thermoplastic resin tube by the ring 4 and the rubber annulus 5.