A reinforcing bar binding machine includes a first movable gripping member that is displaced in a direction to come in contact with and separate from one side of a fixed gripping member. A second movable gripping member is displaced in a direction to come in contact with and separate from the other side of the fixed gripping member; and a bending portion brings the first movable gripping member and the second movable gripping member into and out of contact with the fixed gripping member. The fixed gripping member includes a shaft that rotatably supports the first movable gripping member and the second movable gripping member. In addition, the bending portion includes an opening and closing pin that pushes an opening and closing guide hole provided in the first movable gripping member and an opening and closing guide hole provided in the second movable gripping member.