This production method is for disc-shaped polymer particles having an average aspect ratio of 1-1.3. The method comprises conducting, in a solvent, solution polymerization of monomers including a hydrophobic unsaturated monomer which is liquid at 25° C., in the presence of a polymerization initiator, a surfactant, and/or a polymer stabilizer, wherein a solvent mixture containing water, a hydrophilic organic solvent, and a hydrophobic organic solvent is used as the solvent, and, as the polymerization initiator, one or more polymerization initiators soluble in at least one of water, the hydrophilic organic solvent, and the hydrophobic organic solvent are used as a combination that is soluble in all of water, the hydrophilic organic solvent, and the hydrophobic organic solvent, such that the hydrophobic unsaturated monomer, water, the hydrophilic organic solvent, and the hydrophobic organic solvent are mixed at a predetermined ratio.