A method for producing a polymerizable composition for optical materials; wherein the step for preparing the polymerizable composition for optical materials comprises a step for preparing a polythiol compound containing, as a main component, one kind or two or more kinds selected from the group consisting of compounds represented by the following formulae to, and a step for preparing the polymerizable composition for optical materials from the polythiol compound containing, as a main component, one kind or two or more kinds selected from the group consisting of compounds represented by the following formulae to; wherein the step for preparing the polythiol compound containing, as a main component, one kind or two or more kinds selected from the group consisting of compounds represented by the following formulae to comprises: a step for reacting 2-mercaptoethanol with an epihalohydrin compound represented by the following formula to obtain a compound represented by the following formula; (wherein X represents a halogen atom) a step for reacting the compound represented by formula with sodium sulfide to obtain a polyalcohol compound represented by the following formula; a step for reacting the polyalcohol compound represented by formula thus obtained with thiourea in the presence of hydrogen chloride to obtain an isothiuronium salt; a step for adding, while maintaining a reaction solution containing the isothiuronium salt thus obtained at a temperature of 20°C to 60°C, aqueous ammonia to the reaction solution within 80 minutes, thereby hydrolyzing the isothiuronium salt to obtain a polythiol compound containing, as a main component, one kind or two or more kinds selected from the group consisting of compounds represented by the following formulae to; and a step for adding hydrochloric acid which is concentration of 30% to 36% to the solution containing the polythiol compound thus obtained, washing the solution at a temperature of 30°C to 55°C to purify the polythiol compound containing, as a main component, one kind or two or more kinds selected from the group consisting of compounds represented by the formulae to. a step for reacting 2-mercaptoethanol with an epihalohydrin compound represented by the following formula to obtain a compound represented by the following formula; (wherein X represents a halogen atom) a step for reacting the compound represented by formula with sodium sulfide to obtain a polyalcohol compound represented by the following formula; a step for reacting the polyalcohol compound represented by formula thus obtained with thiourea in the presence of hydrogen chloride to obtain an isothiuronium salt; a step for adding, while maintaining a reaction solution containing the isothiuronium salt thus obtained at a temperature of 20°C to 60°C, aqueous ammonia to the reaction solution within 80 minutes, thereby hydrolyzing the isothiuronium salt to obtain a polythiol compound containing, as a main component, one kind or two or more kinds selected from the group consisting of compounds represented by the following formulae to; and a step for adding hydrochloric acid which is concentration of 30% to 36% to the solution containing the polythiol compound thus obtained, washing the solution at a temperature of 30°C to 55°C to purify the polythiol compound containing, as a main component, one kind or two or more kinds selected from the group consisting of compounds represented by the formulae to.