A method of fiber laser processing of thin film deposited on a substrate includes providing a laser beam from at least one fiber laser which is guided through a beam-shaping unit onto the thin film. The beam-shaping optics is configured to shape the laser beam into a line beam which irradiates a first irradiated thin film area Ab on a surface of the thin film, with the irradiated thin film area Ab being a fraction of the thin film area Af. By continuously displacing the beam shaping optics and the film relative to one another in a first direction at a distance dy between sequential irradiations, a sequence of uniform irradiated thin film areas Ab are formed on the film surface defining thus a first elongated column. Thereafter the beam shaped optics and film are displaced relative to one another at a distance dx in a second direction transverse to the first direction with the distance dx being smaller than a length of the irradiated film area Ab. With the steps performed to form respective columns, the elongated columns overlap one another covering the desired thin film area Af. The dx and dy distances are so selected that that each location of the film area Af is exposed to the shaped laser beam during a cumulative predetermined duration.