A connector is provided in which, only inserting a plug and a socket with each other, a plug body and a socket body are rotated relative to each other around a center axis line to a regular position, and the overall outer diameter of the connector can be reduced.An outward protrusion 9 is provided on an outer peripheral surface of the distal end portion of an insertion portion 7 of a plug body 4, a plurality of inward ridges 17 extending in an axial direction facing are provided on the inner surface of a cylindrical portion 8 of a socket body 6, a groove 16 through which the outward protrusion 9 can pass is formed between each of the adjacent ridges 17, and an inclined cam surface 18 is provided on the inner surface of the cylindrical portion 8 closer to the proximal end portion than the ridge 17, so that the protrusion 9 can slidably contacts and guides the plug body 4 to a regular position.