To provide a machine component such as a gear to be used after having been carburized, which has both an advantage of having been surface-hardened by carburization and an advantage of having been surface-strengthened by a shot-peening technique.

A steel material to be carburized has an alloy composition comprising, by wt.%, 0.10 to 0.30% C, 0.50 to 3.00% Si, 0.30 to 3.00% Mn, 0.030% or less P, 0.030% or less S, 0.01 to 1.00% Cu, 0.01 to 3.00% Ni, 0.30 to 1.00% Cr, 2.00% or less Mo, further one or more elements among 0.20% or less Al, 0.20% or less Nb, 0.20% or less Ti, 0.050% or less N and 0.01% or less B, while satisfying the condition of [Si%]+[Ni%]+[Cu%]-[Cr%]0.30, and the balance Fe with unavoidable impurities. The method for manufacturing the component includes forming the steel material to be carburized having the above composition into the component shape, vacuum-carburizing the component, quenching it, and then shot-peening it.