PURPOSE: To obtain a composite polymer having excellent processability and transparency, by mixing a particulate vinyl chloride copolymer, an ethylene-vinyl acetate-CO terpolymer and/or a thermoplastic polyurethane, and a specified solvent in an aqueous medium, and dehydrating and drying the mixture.

CONSTITUTION: A vinyl chloride copolymer (A) with an average particle diameter of 40W200μm and a degree of polymerization of 300W5,000, containing 20W 98wt% vinyl chloride; an ethylene-vinyl acetate-CO terpolymer consisting of 40W 80wt% ethylene, 10W60wt% vinyl acetate, and 3W30wt% CO, and/or a thermoplastic polyurethane with a molecular weight of 300 or higher (B); and a solvent (C) which is not compatible with water and is a poor solvent for component A and a good solvent for component B (e.g. vinyl chloride), in an amount of 50pts. wt. or more based on 100pts.wt. component B, are mixed at a temperature from ordinary temperatures to 80°C for 30minW3hr in an aqueous medium (D) in an amount of 50W500pts.wt. based on 100pts.wt. A+B. After component C is removed, the mixture is dehydrated and dried.