PURPOSE: To make a bite into the circumferential surface of a tube on a pallet wall constantly maintainable by trimming a stepped diametral expensing chamber of a joint body with a sealing member and a collet-form holding member, and installing an engaged wall integrally in this holding member and simultaneously setting up a step part being almost inscribed to this engaged wall, in the joint body.

CONSTITUTION: A joint body 1 is provided with a stepped with a stepped diametral expanding chamber 2 ranging to a flow hole in the axial center, and a diametral contractive taper surface 1' is formed in a rear circumferential end side in an inner aprt of the diamtral expanding chamber 2. A ring elastic sealing member 3 sticking close to the circumferential surface of a tube T to be connected to an inner part of the diametral expanding chamber 2 is fitted in this joint body 1, while a holding member 4 with a taper surface 4''' engaging with the taper surface 1' and a pallet wall 4; is installed at the back of this sealing member 3. At a front side wall of the diametral expanding chamber 2 at the side of the joint body, an amount of biting into a tube peripheral surface at the pallet wall 4' by means of engagement of the engaged wall 4'' is maintained constant by a ring step part 1'' projectingly installed to the rear being almost inscribed to the engaged wall 4'' of the holding member 4.