PURPOSE: To manufacture the steel having excellent strength and toughness in high heat economic efficiency and high productivity by casting and solidifying a molten steel, thereafter subjecting it to specified rolling in a specified temp. area and thereafter executing specified cooling treatment.

CONSTITUTION: A molten steel is cast and solidified, and rolling of ≥30% cast thickness is thereafter executed in the temp. area of the recrystallization- formable lower limit temp. or above in austenite while the steel lies in the Ar3 point temperature or above. As the compsn. of the above molten steel, the one contg., by weight, 0.10 to 0.20%C, ≤0.025% S, 0.01 to 0.80% Si, ≤0.1% Al and 0.20 to 2.00% Mn, furthermore contg., at need, 0.002 to 0.1% Nb and/or 0.002 to 0.1% Ti, moreover contg. one or more kinds among ≤1% Cu, ≤0.1% Zr, ≤10% Ni, ≤0.008% Ca, ≤1% Cr, ≤0.006% B, ≤1% Mo, ≤0.01% REM and ≤0.2% V and the balance Fe with inevitable components is preferably regulated. After executing the above rolling, the rolled stock is continuously cooled in the temp. area from the Ar3-100°C or above to ≥100°C at 1.5 to 40°C/sec cooling rate. In this way, the steel having excellent strength and toughness can efficiently be obtd. at low cost.