To provide a method for producing a methacrylate polymer having high stereoregularity in a high yield.

A methacrylate is polymerized by using a catalyst system comprising (a) an organomagnesium compound represented by the formula: RMgX (wherein R is a hydrocarbon group; and X is a halogen atom) and (b) at least one compound selected from among compounds each having an organic acid group, bipyridine compounds, and dithiol compounds.