The present invention relates to a polyurethane urea elastic yarn having improved dyeability and a manufacturing method therefor. Through a process of forming a prepolymer by mixing polyethyleneglycol with polyol and then adding diisocyanate to the same in a prepolymer manufacturing step during the manufacture of a polyurethane urea elastic yarn, the hydrophilicity of the polyurethane urea elastic yarn is improved such that the accessibility of an acid dye is enhanced, thereby enabling the dyeability of the polyurethane urea elastic yarn to be enhanced and an advantage of dye color deepening of a fabric, in which nylon and a polyurethane urea elastic yarn are knitted together, to be expected.