PURPOSE: To provide high strength and high toughness non-heat treated steel capable of obtaining toughness comparable to that of a heat treated material in spite of its high strength and having high endurance limit ratio.

CONSTITUTION: The compsn. contg., by weight, 0.10 to 0.35% C, 0.05 to 0.50% Si, 2.0 to 3.0% Mn, 0.3 to 1.5% Cr and 0.07 to 0.50% V and furthermore contg., at need, one or ≥ two kinds among ≤0.05% Mo, ≤0.05% Nb and ≤0.05% Ti as well as contg., at need, ≤0.15% S, ≤0.30% Pb, ≤0.005% Ca, ≤0.30% Bi and ≤0.30% Te, and the balance Fe with impurities is used. I this way, the high strength and high toughness non-heat treated steel having ≥95% bainitic area ratio and ≥90kgf/mm2 tensile strength can be obtd.