A ratchet buckle assembly which tightens a strap for binding a load. The assembly has its body 1 and handle 2 improved in mechanical strength, and prevents the load from being released from the strap by accident when the assembly is in its locked condition. A ratchet drive lever 4 is easily handled, and stabilized in its slidable operation. The assembly comprises: the body 1 constructed of arms 1a, 1b and a plate interposed therebetween; a winding shaft 7 constructed of plates 7a, 7b and supported between the arms 1a, 1b; a handle 2 constructed of arms 2a, 2b, a plate interposed therebetween and grips 10, 11; ratchet wheels 5a, 5b mounted on the shaft 7, wheel 5a being interposed between the arms 1a and 2a, the other wheel 5b being interposed between the arms 1b and 2b; a ratchet 3 for preventing the wheels 5a, 5b from rotating; and the lever 4 for rotatably driving the wheels 5a, 5b so that the strap is wound on the shaft 7.