The trimmer includes: a pusher 2 that pushes the bound material 1; a pusher moving device that moves the pusher; a positioning part 111 that positions the bound material pushed by the pusher; an allowable position memory that memorizes an allowable position range relevant to the pusher; an allowable reaction force memory that memorizes an allowable reaction force range relevant to the pusher; and a determiner that determines whether a length of the bound material is normal or abnormal. The determiner determines that: the length L of the bound material is normal; or the length L of the bound material is abnormal.

The trimmer includes: a pusher 2 that pushes the bound material 1; a pusher moving device that moves the pusher; a positioning part 111 that positions the bound material pushed by the pusher; an allowable position memory that memorizes an allowable position range relevant to the pusher; an allowable reaction force memory that memorizes an allowable reaction force range relevant to the pusher; and a determiner that determines whether a length of the bound material is normal or abnormal. The determiner determines that: the length L of the bound material is normal; or the length L of the bound material is abnormal.