PURPOSE: To provide parts made of carburized steel excellent in pitting resistance and most suitable for parts for machine structural use.

CONSTITUTION: A steel having a composition which consists of, by weight, 0.05-0.3% C, 0.05-2% Si, 0.3-2% Mn, 2-8% Cr, ≤0.03% S, 0.015-0.06% Al, 0.005-0.02% N, and the balance Fe with inevitable impurities and where the contents of P and O among the inevitable impurities are controlled to ≤0.02% and ≤0.002%, respectively, is used as a stock. The parts made of this stock are subjected to carburizing or carbonitriding treatment and then to quench-and- temper treatment, by which carbides or carbonitrides of ≤5μm average grain size are precipitated in the surface layer part. Further, the area ratio of these carbides or carbonitrides is regulated to 2-60%, and further, those having a composition of M7C3 comprise ≥30% of these carbides and carbonitrides.