The present invention provides a buckle having a simple structure to increase efficiency of an assembling operation and desirable operability wherein engagements of plugs with a socket are reliably carried out. The buckle comprises a pair of plugs and a socket. Each the plug has a strap attaching portion, a tongue formed to project from the strap attaching portion to be inserted into the socket, and an engaging portion. The socket is formed with inserting portions into which the tongues are inserted respectively, and fixed engaged portions with which the engaging portions are engaged. An operating portion is formed separately from the socket between the engaged portions for displacing the engaging portions to-disengage engagements of the engaging portions with the engaged portions. The operating portion comprises an operating chip exposed to an outer surface of an operating hole of the socket, pushing portions integrally formed on a rear face side of the operating chip, and a locking portion to be locked at the socket. Resilient portions are formed on at least one of the operating chip and the socket so as to abut on the other of the operating chip and the socket and to bias the operating portion outward.