The present invention relates to a device for adjusting the width of a paper web at a rotary lithographic press and the object of the present invention is to prevent ink or specks of paper from becoming attached to contact parts of a pressing member so as to contaminate the surface of the paper web, and to enable straightforward fitting and removing of a rotatable pressing member. This configuration is therefore provided with one or more pressing members 1 with a plurality of contact members 11 provided integrally in a rotating manner so as to be capable of being mutually separated along the widthwise direction of a paper web W, a support shaft 20 supporting the pressing member(s) 1 in a rotatable manner, wavy surface adjustment means 2 capable of moving the support shaft 20 towards and away from the surface of the paper web W, and pressing member rotation drive means 4 for simultaneously rotating and driving the pressing member 1. It is then possible to move at least one of the pressing members 1 towards and away from the surface of the paper web W and rotational drive is possible in such a manner that rotational speed of the peripheral surfaces of the contact member 11 of the pressing member(s) 1 may be different to the speed of travel of the paper web W.