An installation groove is formed on an outer circumferential surface of a tube joint body, into which a fluid tube is inserted. An annular fixing ring is installed through interaction with the installation groove. A cylindrical guide member is arranged inside of the body. A chuck is provided that engages with an outer circumferential surface of the fluid tube, thereby retaining the fluid tube. When a fastening pawl of the chuck bites into the outer circumferential surface of the fluid tube, the guide member is pressed radially outwardly by the chuck, with the tube joint body being interposed between the guide member and the fixing ring.