STEEL FOR MACHINE STRUCTURES

A steel for machine structural use is provided which is excellent in machinability and rusting characteristics, and with which machine components that are excellent in rolling contact fatigue properties are obtained. The steel for machine structural use according to the present embodiment has a chemical composition which consists of, in mass%, C: 0.30 to 0.50%, Si: 0.01 to 0.80%, Mn: 0.20 to 2.00%, P: 0.030% or less, S: 0.010 to 0.100%, Pb: 0.010 to 0.100%, Al: 0.010 to 0.050%, N: 0.015% or less, O: 0.0005 to 0.0030% and Cr: more than 0.70% to 2.00%, with the balance being Fe and impurities, the chemical composition satisfying Formula (1). The total number of specific inclusions included in the steel which are any of MnS inclusions, Pb inclusions and composite inclusions containing MnS and Pb and which have an equivalent circular diameter of 5 µm or more is 40 per mmor more.Where, a content (mass%) of a corresponding element is substituted for each symbol of an element in Formula (1).