Laser system for the generation of windows in security paper (10, 10') that comprises: - guiding and transporting means (140, 150, 151) of the security paper along a path through the interior of said laser system; - laser cutting means along said path of the security paper (10, 10'); and - suction means comprising at least one suction mouth, located along said path of the security paper (10, 10'); - laser control means configured so said laser cutting means generate the window in the security paper (10, 10') by means of a continuous cut according to a pre-established pattern and a pre-established cutting area; said suction means being located below the security paper (10, 10') below said cutting area to suction the window cut from the security paper after the cut carried out by the laser cutting means; characterized in that said laser cutting means comprise at least one laser head and one scanner per each laser head, and in that the system also comprises a high-resolution encoder and a plurality of optical sensors located in the path of the security paper (10, 10') before the cutting area, said plurality of sensors providing information about possible deviations of the security paper along the path; wherein a first sensor of said plurality of sensors is configured to detect an edge of the security paper (10, 10'), said first sensor providing information about the transverse deviation of the security paper; and a second sensor of said plurality of sensors is configured to detect a reference mark arranged along the security paper (10, 10'), said second sensor providing information about the longitudinal deviation of the security paper. - guiding and transporting means (140, 150, 151) of the security paper along a path through the interior of said laser system; - laser cutting means along said path of the security paper (10, 10'); and - suction means comprising at least one suction mouth, located along said path of the security paper (10, 10'); - laser control means configured so said laser cutting means generate the window in the security paper (10, 10') by means of a continuous cut according to a pre-established pattern and a pre-established cutting area; said suction means being located below the security paper (10, 10') below said cutting area to suction the window cut from the security paper after the cut carried out by the laser cutting means; said laser cutting means comprise at least one laser head and one scanner per each laser head, and in that the system also comprises a high-resolution encoder and a plurality of optical sensors located in the path of the security paper (10, 10') before the cutting area, said plurality of sensors providing information about possible deviations of the security paper along the path; wherein a first sensor of said plurality of sensors is configured to detect an edge of the security paper (10, 10'), said first sensor providing information about the transverse deviation of the security paper; and a second sensor of said plurality of sensors is configured to detect a reference mark arranged along the security paper (10, 10'), said second sensor providing information about the longitudinal deviation of the security paper.