A natural oil-based toner resin for producing toner in developing electrophotographic image comprising a copolymer of unsaturated polyester resins and vinyl monomers, wherein the polyester resins have a molecular weight of 500 to 30000 and obtained from polycondensation between a polycarboxylic acid, a natural oil or derivative thereof and a polyol. The toner resin in emulsion form is mixed with fine suspensions or emulsions of a colourant and a charge control agent; and a flocculating agent is incorporated therein to induce aggregation for forming particles of desired sizes, and subsequently the temperature is suitably raised to cause coalescence to produce raw toner particles of regular shape and smooth surface. The raw toner particles are washed and dried, and treated with suitable additives to produce the finished product of chemically produced toner.