PURPOSE: To stably produce the good-quality thick steel plate which is free from internal porous shrinkage cavity by rolling the thick steel plate over two steps at different rolling shape ratios in an austenite unrecrystallization temp. at the time of producing the thick steel plate by rolling from a steel ingot.

CONSTITUTION: A stock billet 2 is rolled by using rolling rolls 1 of a radius Rmm in the austenite unrecrystallization temp. region at the time of producing the thick steel plate of ≥100mm thickness by hot rolling of the steel ingot or cast billet. The billet is rolled in one to several passes at ≤0.4 rolling shape ratio (ld/hm) as the ratio between the contact projection length of the rolls ld and the mean plate thickness hm and is then subjected to at least 1 pass of the rolling at >0.7 rolling shape ratio at the time of rolling the billet 2 from the thickness h1 of the billet at the inlet side of the rolling rolls 1 to the thick steel plate of the thickness h2 at the outlet side of the rolls, by which the porous shrinkage cavity by the segregation in the central part are press- welded and the thick steel plate having the good quality is produced at a good yield.