PROBLEM TO BE SOLVED: To provide a water-soluble polymer pigment dispersant which finely disperses a pigment and can form a coating film having good storage stability, a proper range of viscosity, good hue and excellent water resistance, and to provide an aqueous composition containing the water-soluble polymer pigment dispersant.SOLUTION: There is provided a water-soluble polymer pigment dispersant containing a copolymer which comprises: styrene (A); a (meth)acrylic acid alkyl ester monomer (B) having an alkyl group having 1 to 10 carbon atoms; a monomer (C) which is a sodium salt of organic sulfonic acid-based vinyl monomers, an alkali metal salt such as a potassium salt, and an alkali metal salt such as an alkali earth metal sa a monomer (D) such as polyoxyethylene nonylpropenylphenyl ether, polyoxyethylene nonylpropenylphenyl ether ammonium sulfate and polyoxyethylene nonylpropenylphenyl ether sodium sulfate; and a monomer (E) such as sodium or ammonium (meth)acrylate as essential constituting components.
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