Disclosed is an oil composition comprising a lubricant oil base oil and an alkylene oxide adduct of a hydroxy acid, wherein the alkylene oxide adduct has a hydrophile-lipophile index of 8 to 14. The oil composition can be used in a trace amount oil supply type cutting/grinding processing. Also disclosed is a trace amount oil supply type cutting/grinding processing method characterized by comprising a step of supplying the oil composition in the form of a mist to a part to be processed in a material of interest together with a compressed fluid.