The application relates to a method for laser-based machining of a flat substrate (1), in particular of a wafer or glass element, to separate the substrate into a plurality of sections, in which the laser beam (2a, 2b) of a laser (3) for machining the substrate (1) is directed at the latter, characterized in that by means of an optical arrangement (6), which is positioned in the beam path of the laser (3), a laser beam focal line (2b) that is extended as viewed along the beam direction is formed on the beam output side of the optical arrangement (6) from the laser beam (2a) shone onto the optical arrangement (6), wherein the substrate (1) is positioned relative to the laser beam focal line (2b) in such a manner that an induced absorption is produced in the material of the substrate in the interior of the substrate (1) along a section (2c) of the laser beam focal line (2b) that is extended as viewed in the beam direction, by means of which absorption an induced crack formation takes place in the material of the substrate along said extended section (2c).