The present invention is a simple structure of one pair in the plug at the same time the operability with features that are disengaged from the socket and coupled to provide a good buckle (buckle). Buckle is to include the plug 10 and the socket 20 of one pair. To a fastening portion 16 formed in the installation (舌) unit 14, a front end (先端 部) of the tongue (14) which is inserted in each, the plug 10, socket 20. And socket 20, each tongue 14 is inserted into the insertion portion 22, a fixed-be-engaged portion 26 of the engaging portion 16 of the plug 10 is coupled to the insertion part 22, which is, to install the operation unit 24 to the engaging portion 16 provided between the engaged portion 26 releases the engagement with the position change sikieo coupling portion 16 and the engaged portion 26. And the operation unit 24 is an operation section (operating chip) (24a) and, the operation pressure is formed integrally with a back surface of the piece (24a) pressure portion (24b) exposed to the outer surface of the socket 20, the operation piece integrally from the rear face (裏面) side of the socket 20 from (24a) of the insertion part 22, the elastic portion 25 of the one pairs located mutually symmetrically with respect to the said operating part (24a) extending towards the inside It will be included.