PURPOSE: To produce a thick steel plate for a structural member having good strength and toughness, at the time of subjecting an ingot having a specified componental compsn. to rolling, by executing the rolling and repeated bending under specified conditions and imparting cumulative quantity of strains shown by the inequality thereto.

CONSTITUTION: An ingot or a slab is cast from a steel contg., by weight, 0.02 to 0.30% C, 0.01 to 2.0% Si, 0.30 to 3.5% Mn and 0.003 to 0.10% Al, and the balance Fe with inevitable impurities. Next, at the time of subjecting the same ingot or slab to rolling directly or after reheating, the rolling is finished in the temp. range of the Ar3, point or above, and successively, it is subjected to repeated bending in the unrecrystallized temp. range of austenite and is imparted with the cumulative quantity of strains within the range shown by the inequality [: the total (%) of strains imparted to the surface layer part of the plate thickness by the repeated bending, R: the cumulative rolling reduction (%) in the rolling in the unrecrystallized temp. range, n: the number of times in the repeated bending and T: the surface temp. (°C) of the thick steel plate at the time of executing the repeated bending].