Provided is a method for producing a molded product comprising preparing a polymerizable composition for optical materials and curing the polymerizable composition for optical materials to produce the molded product. The preparation of the polymerizable composition comprises preparing a polythiol compound containing, as a main component, one kind or two or more kinds selected from a defined group of compounds, and preparing the polymerizable composition from the polythiol compound. The preparation of the polythiol compound comprises reacting 2-mercaptoethanol with a defined epihalohydrin compound to obtain a defined compound, reacting the defined compound with sodium sulfide to obtain a defined polyalcohol compound, reacting the polyalcohol compound with thiourea in the presence of hydrogen chloride to obtain an isothiuronium salt, adding aqueous ammonia to a reaction solution containing the isothiuronium salt thereby hydrolyzing the isothiuronium salt to obtain the polythiol compound and purifying the polythiol compound with hydrochloric acid.