Abstract: A coupling comprises a socket and a plug removably connected thereto. In the socket and the plug, a first fluid passage and a second fluid passage are formed, respectively. An on-off valve chamber, a first packing chamber and a second packing chamber are arranged in succession in the socket. An elastic packing member and a sealing member are disposed in the first and second chambers, respectively, so that their adjacent surfaces are pressed against each other. An on-off valve chamber having a cylindrical valve body is located in the on-off valve chamber in such a manner that the valve body can approach the first packing chamber and recede from it. It is urged toward the packing by a compression coil spring. An abutment which abuts against the packing is formed on an intermediate portion of the valve body.