A vinyl monomer alone, or a mixture of a vinyl monomer and at least one comonomer copolymerizable with said vinyl monomer and having a faster rate of polymerization than the rate of polymerization of the viny monomer, is emulsion-polymerized in an aqueous medium in the presence of a surface active agent and a pigment and, if required, other additives, under vigorous stirring. The polymer particles are substantially spherical. They do not contain interconnected pigment particles on the surface thereof but rather the pigment particles are substantially uniformly distributed in the interior of the polymer particles. There is obtained a powder composition adapted for electrostatic spray coating. When an agent for preventing thermal cracking is added to the emulsion polymerization reaction mixture after the completion of polymerization, there is obtained an electrostatic spray coating powder paint composition which does not become deteriorated if the coating film is heated at high fusing temperatures.