[en] PROBLEM TO BE SOLVED: To provide a novel process for producing a homopolymer, a random copolymer, or a block copolymer having a controlled molecular weight, a narrow molecular weight distribution, a high monomer conversion ratio, and a controlled structure. ; SOLUTION: The polymer having a controlled molecular weight, a narrow polydispersibility, a high monomer conversion ratio, and a controlled structure is produced by polymerizing a vinyl monomer during the formation of a mixture of a hindered secondary amine and an oxidizing agent at a relatively low temperature in a short reaction time. It is unnecessary to add a free radical initiator before polymerization. Further, it is unnecessary to preliminarily react the secondary amine with the oxidizing agent before adding the monomer.