To provide a polymerization method of a polar compound using a new polymerization catalyst.

The polymerization method of the polar compound comprises contacting (A) an initiator consisting of an organic silicone compound represented by formula (I): ArSi(SiR3)3 (I) (wherein Ar indicates an aryl group that may be substituted and R indicates an alkyl group), (B) a polar compound that has a carbon-carbon double bond in the position to a carbonyl, nitrile, nitro, sulfonyl or phosphoryl group, and (C) at least one co-catalyst selected from an onium compound that has fluorine, azide, cyanide, carboxylate or a salt of these with a conjugated acid as the counteranion; an alkali metal fluoride; or an alkali metal bifluoride; and a Lewis acid.