PURPOSE: To produce a thick steel for low temp. use having brittle fracture propagation stop characteristics at ≤-50°C and to increase the safety of structure such as LPG tank.

CONSTITUTION: A slab having a compsn. contg., by mass, 0.03 to 0.10% C, 0.03 to 0.60% Si, 0.70 to 2.0% Mn, 0.01 to 0.08% Al, 0.005 to 0.03% Ti and 0.002 to 0.007% N, furthermore contg. one or ≥ two kinds selected from 0.01 to 0.05% Nb, ≤1.0% Ni, ≤0.003% B, 0.0005 to 0.005% Ca and 0.0005 to 0.001% rare earth metals, and the balance Fe with inevitable impurities is heated to 950 to 1150°C, is subjected to rolling reduction at ≥50% cumulative draft in the unrecrystallized temp. range, is thereafter directly hardened from the Ar3 point to the Ar3 point +50°C at ≥20°C/s cooling rate to ≤150°C and is thereafter tempered at 500°C to the Ac1 point. Furthermore, after the tempering, rolling reduction is executed at ≤500°C at 1 to 5% cumulative draft.