Abstract: First and second arms have first and second retaining members, respectively. A switching mechanism switches a retained state of a first position of a tying medium between first and second states. In the in and second states, the first position is retained by the first and second retaining members at first and second retain in positions, respectively. A loop retaining member retains a hop around the second arm in a path extending from the first retaining position through second and third positions to a fourth position of the tying medium. The second position intersects the third position as a result of the loop such that the third position is closer to the first retaining position than the second position in the path. A moving portion moves the loop relative to the second arm to change a relative positional relationship between the hop and the first position on the path.