PROBLEM TO BE SOLVED: To obtain a de-scaling device which improves the frequency of crack applying onto a scale without largely changing a process and which realizes the high sped processing speed by irradiating a hot rolling steel sheet with a laser beam on a stage before transferring it to a scale breaker and applying a laser beam irradiation mark on the scale. SOLUTION: In the stage before a hot rolling steel sheet 4 is transferred in a scale breaker 2, the hot rolling steel sheet 4 is irradiated with a laser beam 1 and seam-like irradiation mark as formed by a sewing machine is applied to a scale on the hot rolling steel sheet 4. The hot rolling steel sheet 4 is succeedingly passed through, by being bent by the scale breaker 2, stripping of the scale is advanced from the hot rolling steel sheet 4 making the seam part as the starding point. By applying the seam at a proper interval, the scale after passing through the scale breaker 2 is worn out with cracks and it is made in the state just before being stripped away. Further, by passing through a pickling tank 3 succeedingly, the pickling liquid enters from stripped parts and an FeO layer of the scale lowest layer is corroded and stripped.
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