To eliminate a partially neutral area on a finished packaging paper.

This cutting device which performs a trimming of a package of printed papers for a packaging machine has a cutting unit consisting of an upper part 15 and a lower part 16, and at least one of those two parts 15, 16 can move upward or downward to a path of a continuous paper material 12 being equipped with a printed part which is separated by a neutral strip 29, which is let off from a rolled paper, and is bonded with an adhesive in the lateral direction and as much as in the longitudinal direction possible, and has a flat tubular shape. One of the two parts 15, 16 of the cutting unit supports two blades 25 which are apart by the same distance as the width of the strip, and the two blades 25 relatively work with two opposite blades 45 being arranged on the other part. Then, an elastic pressure element 36 is positioned at least at one part of the cutting units 15, 16, and works to stop the paper material 12 while a cutting is perforemd to the strip. Also, an element 43 being removable when the width of the strip changes, is provided in order to change the distance between the blades and the opposite blades.