To obtain the subject resin, hardly producing large particles and good in fluidity without causing scale sticking to a polymerizer by continuously adding a dispersion prepared by dispersing a silicate in an aqueous medium to the polymerizer.

When the suspension polymerization is carried out by continuously adding (A) vinyl chloride monomer alone or a mixture of the component A with (B) a polymerizable monomer copolymerizable with the component A into an aqueous medium containing (C) a dispersing agent, (D) a dispersion obtained by dispersing a silicate (preferably calcium silicate, talc or mica) in the component C is continuously added to a polymerizer. A raw material mixture containing the components A, D and C is preferably continuously added and the mixture is heated at a temperature within the range of (T-10°C) to (T+5°C) based on a prescribed polymerization temperature (T) and fed to the polymerizer at this time.