PURPOSE: To provide a sizing agent composition composed of an emulsion produced by the copolymerization or graft-polymerization of a specific monomer or a polymer, etc., in the copolymerization of a lower fatty acid vinyl ester and effective in getting finished clothes having stiffness and excellent feeling to the skin.

CONSTITUTION: A sizing agent base is synthesized by copolymerizing a monomer or polymer of a carboxylic acid alkoxyalkyl ester expressed by formula (R1 is ethenyl, 2-propanyl, etc.; R2 is ethylene, isopropylene, etc.; R3 is 1-3C straight- chain or branched alkyl) in the polymerization of a lower fatty acid vinyl ester (e.g. vinyl acetate) or in the copolymerization of the ester and a monomer copolymerizable with the ester [e.g. methyl (meth)acrylate]. A sizing agent produced by adding a cationic polymer, etc., (e.g. cationic cellulose and cationic starch) to the emulsion of the sizing agent base can give finished clothes having stiffness and good feeling to the skin and the applied sizing agent has high durability on the clothes.