Provided is a composition for optical materials that gives optical materials which can have at least one improved property selected from among satisfactory mold releasability after polymerization and curing, unsusceptibility to separation from the mold during polymerization and curing, transparency, and low-level striae. The present invention further provides a compound represented by formula (1). The composition for optical materials comprises the compound represented by formula (1) and a compound represented by formula (2). (In formula (1), X1 and X2 represent O or S, provided that both X1 and X2 are O or that X1 is O and X2 is S.)