To enhance the certainty of operation by extending the stroke of a wire twisting device in a reinforcement binder.

A compression spring 34 and a flanged pin 35 attached to a threaded shaft 32 are inserted into a cylinder part 33a formed in the rear end face of the shaft 33 of a wire twisting device 31, and the threaded shaft 32 is connected to the shaft 33 by a locking ring 36. The shaft 33 is free to rotate and can move back and forth within the range of the axial length of the flanged pin 35. A pair of hook levers 39 is pivotally attached to the front of a sleeve 38 coupled to a sleeve nut 37, and the guide groove of each hook lever 39 is engaged with the front guide pin 41 of the shaft 33. In the advance stroke of the sleeve 38, the shaft 33 also advances by a fixed distance, and since the hook levers 39 go into a closure stroke after they have advanced by a fixed distance while kept apart, the range in which a wire can be captured is increased.