Disclosed is a triazine ring-containing hyperbranched polymer containing a repeating unit structure represented by the expression (1). By this means, it is possible to achieve a triazine ring-containing polymer which, alone, has high heat resistance, high transparency, high refractive index, high light resistance, high solubility, low volume shrinkage without adding metal oxides; and also a membrane-forming composition containing the same.
(In the formula, R and R′ represent independently a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, or an aralkyl group, and A represents an alkylene group optionally having a branched or alicyclic structure of 1 to 20 carbon atoms.)