Abstract: Slitting unit forming part of a machine for production of carton blanks, in particular blanks made of cardboard or corrugated cardboard. The unit (2) comprises working wheels (12, 24, 25, 28) which are opposite in pairs, one wheel in at least one pair (24) being made with at least one slitting knife (26) extending over a part of the periphery of the wheel while the periphery of the other wheel in said pair is made with a slot for receiving the knife. The unit also comprises a vacuum belt (6) running adjacently to each slitting-wheel pair (24; 25) for securing and feeding the blanks (10). The wheels (24; 25) in each slitting-wheel pair are mounted in an upper and, respectively, a lower stand unit (3, 4) at least a portion of that part of one stand unit (4) which faces towards the other (3) being made in the form of a vacuum box.