PURPOSE: To improve pitting resistance, bending fatigue limit, and rolling fatigue limit by subjecting a steel material to carburizing treatment to a carbon potential in a specific high carbon region, to temporary cooling down to a temp. not higher than the Ar transformation point, and then to specific heat treatment.

CONSTITUTION: A steel material is subjected to high carbon carburizing treatment at about 930°C while setting a carbon potential to a high carbon region of 0.9-1.2%. Then, the steel material is cooled down to a temp. not higher than the Ar1 transformation point, e.g. about 160°C to undergo carburizing and quenching. Subsequently, the steel material is reheated to 850°C, successively held in a oil or salt bath at 200-230°C for 0.5-2hr to undergo hardening, and then cooled. By this method, deterioration in strength can be prevented by forming a matrix into high carbon martensite, and pitting resistance and bending fatigue limit can be improved.