[Problem] To provide a polymer matrix which not only can inhibit an organic nonlinear optical compound from undergoing a relaxation from orientation but also can more highly orient the organic nonlinear optical compound and which renders viscosity regulation easy; and to provide a composition comprising the polymer matrix and an organic nonlinear optical compound and an optical material obtained from the composition. [Solution] A composition which comprises: a norbornene imide copolymer having a structural unit represented by formula [1] and a structural unit represented by formula [2]; and an organic nonlinear optical compound. (In the formulae, R1 represents an optionally substituted C1-12 alkyl group or an optionally substituted C6-10 aryl group and L1 represents a C1-30 divalent organic group.)