Abstract: The inner surface of the open end of a socket for a pipe is formed with a taper portion and a lock ring is received on the inner periphery of the taper portion. The outer peripheral portion of the socket corresponding to the taper portion is tapered in the same direction so that the wall thickness of the socket at the taper portion has a suitable value. When a pull-out force acts on a spigot inserted in the socket, the wedge action of the taper portion presses the lock ring against the spigot, whereby the separation is prevented. If an excessive pull-out force acts thereon, the portion of the socket which has the suitable thickness is deformed for radial expansion so as to allow the pull-out of the lock ring. Thereby, the pipe joint and the pipe body are prevented from being broken by the excessive force.