To provide a method for straightening a thick steel plate with a roller leveler, which can effectively prevent the generation of surface defects.

In the method, a pass in which the plate is passed into a roller leveler 1 from a side where a descaling device 2 is equipped is defined to be a straightening pass, and a pass in which the plate is passed from the side where the descaling device is not equipped is defined to be a non straightening pass in which the straightening is not performed. The thick steel plate S after hot rolling is subjected to the straightening pass at least three times. Thereby, the shape defect of flatness etc. is improved, further the release of internal stress is sufficiently performed, to obtain the thick steel plate with no generation of surface defects. Moreover, a horizontal water spray means 4 is arranged in the roller leveler, and by spraying water spray to a leveling roll 1a of the roller leveler and the thick steel plate to be passed, the generation of the surface defect is further suppressed. Moreover, a water spraying device 3 is provided in the side where the descaling device is not equipped, and water may be sprayed to the thick steel plate before passing.