A tube joint comprises a retaining mechanism which retains the locked state by preventing a sleeve from any rotation in the circumferential direction which would be otherwise caused by any unexpected external force. The retaining mechanism includes a ratchet which is provided to surround the outer circumferential surface of a socket body and which is rotatable synchronously with the sleeve, and a coil spring which is interposed between the sleeve and the ratchet and which makes an urging action to cause mutual separation under an action of the spring force.
