PURPOSE: To produce a steel bar which has no dispersion in the hardened structure after high-frequency hardening, by heating a billet contg. specific ratios of C, Si and Mn under specific conditions then subjecting the same to hot rolling to form the specific structure.

CONSTITUTION: The billet contg. by weight % 0.30W0.60% C, 0.10W0.35% Si, and 0.30W2.00% Mn and consisting of the balance iron and unavoidable impurities is heated to the temp. within a (Ac3+50)°CW1,000°C range and is hot rolled. The billet is subjected to intermediate water cooling from about 1,000W850°C in such a manner that the surface layer attains ≤500°C prior to finish rolling. The billet is then subjected to the finish rolling at ≤600°C start temp. of the finish rolling of the surface layer and ≤700°C end temp. of the finish rolling of the surface layer to form the surface layer to the bainite and/or sorbite structure and to form the inside to the fine ferrite/pearlite structure. The steel bar which does to break and bend at the time of stress relieving by a heat treatment and is suitable for the high-frequency hardening is thereby produced.