The present invention provides a poly(meth)acrylate-based viscosity index improver having a core, and three or more arms comprising a polymer chain containing a structural unit represented by general formula (1), one end of said polymer chain being bonded to the core. The weight-average molecular weight (Mw) of the poly(meth)acrylate-based viscosity index improver is at least 100,000, and the ratio of the weight-average molecular weight (Mw) to the the number average molecular weight (Mn) (Mw/Mn) is not more than 1.6. [In formula (1), R1 represents hydrogen or a methyl group, and R2 represents an alkyl group with 1 to 36 carbons.]