To provide a method for producing a new reactive silicon group-having organic polymer, by which the addition (hydrosilylation) reaction of a hydrogenated silicon compound to an organic polymer having side chain-having unsaturated groups is more efficiently promoted.

This method for producing the reactive silicon group-having organic polymer comprises addition-reacting a hydrogenated silicon compound to an organic polymer having unsaturated groups represented by general formula (2): H2C=C(R1)-R2- (2) in the presence of a group 8 transition metal-containing catalyst and a quinone compound. In formula (2), R1 is a 10C hydrocarbon group; and R2 is a 1 to 20C divalent organic group having at least one selected from the group consisting of H, O and N.