The present invention provides a method for manufacturing a polymer by a flow-type reaction. The method includes introducing a liquid A of an anionic polymerizable monomer, a liquid B of an anionic polymerization initiator, and a polymerization terminator into different flow paths, allowing the liquids to flow in the flow paths, allowing the liquid A and the liquid B to join together, subjecting the monomer to anionic polymerization while the liquids having joined together are flowing to downstream in a reaction flow path, and allowing a solution, which is obtained by the polymerization reaction and flows in the reaction flow path, and the polymerization terminator to join together so as to terminate the polymerization reaction and to obtain a polymer having a number-average molecular weight of 5,000 to 200,000. A static mixer is disposed in the reaction flow path, and a polymer having a number-average molecular weight equal to or greater than 2,000 is introduced into an inlet port of the mixer. The present invention also provides a flow-type reaction system suitable for performing the manufacturing method.