To improve the binding finish in a reinforcement binding machine.

A sleeve 5 is meshed with a ball screw shaft 13 driven by a torsional motor. A central clamp plate 2 is loosely connected to the tip of the ball screw shaft. The central clamp plate 2 and clamp plates 3 and 4 arranged on the left and right both sides are housed in the sleeve. Groove cams 9 and 10 are arranged on the left and right clamp plates. The groove cams are engaged with a pair of left and right guide pins 11 and 12 arranged in the sleeve. A wire W is sent out by passing through between the right clamp plate 3 and the central clamp plate 2, and forms a loop, and the tip enters between the left clamp plate 4 and the central clamp plate 2. When the ball screw shaft is rotatably driven, the sleeve advances, and the left and right clamp plates close by the action of the groove cams, and clamp the tip and the rear end of a wire loop.