The perforating device for perforating a web material including a first blade-holder adapted to rotate around a respective first rotation axis and on which at least a first perforating blade is mounted. The device further includes a support beam, on which a plurality of counter-blades are mounted, the support beam being angularly adjustable around a selection rotation axis thereof in a plurality of angular working positions, in each angular working position one of the counter-blades being in an operative position. A movable abutment is also provided adapted to co-act with the support beam. A first actuating device is provided for moving the movable abutment between an active position, where the movable abutment co-acts with the support beam, and an idle position, where the movable abutment is spaced from the support beam. A second actuating device is provided for rotating the support beam in order to arrange it selectively in one of the angular working positions.