The present invention provides a method for producing a vinyl polymer including the steps of polymerizing a vinyl monomer by atom transfer radical polymerization with a transition metal complex as a polymerization catalyst, and bringing the resultant vinyl polymer into contact with an adsorbent in the presence of an oxidizing agent; the vinyl polymer produced by the method; and a reactive composition susceptible to hydrosilylation containing the vinyl polymer produced by the method and having at least one alkenyl group per molecule.