A buckle comprising socket and plug bodies 1, 2 formed of plastics. The socket body 1 has upper and lower plates 5, 6 connected with each other at their one ends. The upper plate 5 has a circular through-hole 9. The lower plate 6 has an inwardly curved locking projection 12 extending from an annular edge portion 10 at the side of the insertion opening and terminating in an engaging edge 11. The plug body 2 has an insertion member 13 including a resilient operating plate 15 which extends from the side of a base end portion 14 of the insertion member 13 and which terminates in a downwardly directed toughing ledge 16 resiliently touching the locking projection 12 when the socket and plug bodies 1, 2 are coupled. <IMAGE>
