PURPOSE: To obtain a thick steel plate having superior brittle crack propagation arresting property and also having superior toughness as inner quality in the central part of plate thickness by specifying the composition of a steel and specially combining respective techniques of rolling, cooling, and dehydrogenation for a steel.

CONSTITUTION: A steel having a composition consisting of, by weight, 0.03-0.25% C, 0.01-0.5% Si, 0.6-1.8% Mn, 0.005-0.1% Al, 0.001-0.010% N, and the balance Fe is rolled. At this time, respective regions of the upper and the lower surface layer part corresponding to 2-33% of the thickness of the steel plate are subjected to the initiation of cooling from a temp. not lower than the Ac3 point at ≥2°C/sec cooling rate and cooled down to ≤Ar3. Recuperation is done after the stoppage of cooling, and finish rolling is performed before the recuperation is completed, by that recuperation is done so that respective temps., after recuperation, in the upper and the lower surface layer region mentioned above of the steel plate after the completion of finish rolling is regulated to a value lower than the Ar3 point or values higher and lower than the Ar3 point around the Ar3 point. Simultaneously, dehydrogenation treatment is done so that hydrogen in the steel, H (ppm), in the central part of plate thickness satisfies H≤(1.08-0.0007 σy), where σy means the yield stress (MPa) of the steel plate at the normal temp.