Disclosed is a lubricating oil composition which includes a diester-based base oil having an asymmetric structure in which the number of carbons of the alkyl chain bound to one ester group with respect to a central atom is two more than that of the alkyl group bound to the other ester group, and which has low viscosity and a comparatively small amount of evaporation at high temperature. When this composition is used for a motor of a small hard disk, power consumption can be reduced and stability at high temperature can be enhanced.