Abstract: A polymerizable composition for polythiourethane optical materials comprising a compound represented by the general formula (1), M(L)n??(1) wherein, in the formula, M is Al, Fe, Cu, Zn, Zr or Bi; L is a dithiocarbamic acid group, a sulfonic acid group, a mono- or di-alkyl phosphoric acid ester group, a substituted acetylacetonato group or a halogen; and n is an integer of 1 to 5, one or two or more isocyanates selected from the group consisting of isocyanate compounds and isothiocyanate compounds, and one or two or more active hydrogen compounds each having a mercapto group. The compounds represented by the general formula (1) exhibit catalytic activity equal to or superior to that of organotin catalysts having been employed as catalysts for the production of polythiourethane optical materials from the past, and have high safety. Further, the thus obtained polythiourethane resins satisfactorily meet the property requirements for optical materials, in particular, excelling in weather resistance.