To provide a nature friendly cross string for binding old paper which binds efficiently the old paper using a small amount of a plastic film material.

This relates to a cross string for binding used paper where two strips of plastic films cross mutually at 90° and the two strips of films are adhered at a part where they superimpose, a cross string for binding old paper where two strips of plastic films are superimposed and the films are linearly adhered at roughly 45° relative to the lengthwise direction of the films in the middle of the films in the lengthwise direction, and a cross string for binding used paper where two strips of plastic films are superimposed, and the films are weakly adhered in the middle of the films in the lengthwise direction.