The objective of the present invention is to provide a method for producing a polymer of a monomer having a vinyl group while reducing a residual amount of a surfactant within the polymer as the target compound and waste water. The method for producing a polymer according to the present invention is characterized in comprising the step of polymerizing a monomer having a vinyl group in an aqueous medium in the presence of a surfactin salt, which is a natural peptide surfactant, and a polymerization initiator, wherein a ratio of the surfactin salt (I) to 100 parts by mass of the monomer is not less than 0.0005 parts by mass and less than 0.1 parts by mass.