Method for manufacturing polymerizable composition for optical material, and polymerizable composition for optical material

This method for manufacturing a polymerizable composition for an optical material includes a step for mixing (A) one or more types of thiol compounds having two or more mercapto groups, (B) a tin compound represented by general formula (1), and (C) one or more types of isocyanate compounds having two or more isocyanate groups, the haze of the polymerizable composition for an optical material obtained by the aforementioned step being 0.05 or less. (1): (R 4 ) c -Sn-X 4-c