The invention provides a lubricant composition capable of favorably preventing the members from causing hydrogen embrittlement-induced flaking when the members are operated under the conditions where the oil film is thin (namely, the metal surfaces considerably come in contact with each other). The lubricant composition used for lubricating the steel mechanical members operated by a rolling motion or rolling-sliding motion is characterized by containing a base oil and additives, the additives including an organic sulfonate rust inhibitor and a load carrying additive.