The present invention is an acrylonitrile-based fiber manufacturing method comprising a step for providing a polymer solution including an acrylonitrile-based copolymer that contains a carboxyl group,a step for producing a spinning solution by mixing 1 to 6 parts by weight of a hydrophilization solution including an organic solvent and ammonia solution in a 95:5 to 60:40 weight ratio to 100 partsby weight of the polymer solution, and a step for spinning the spinning solution. The invention is intended to enhance the stretchability and strength of acrylonitrile-based fibers and inhibit the occurrence of gelling by controlling the viscosity of the spinning solution through a hydrophilization treatment.