A transparent heat-resistant resin optical materials having excellent heat resistance and dynamic characteristics, having negative birefringence and exhibiting a high refractive index and a high Abbe number, especially optical compensating members such as films, sheets and retardation films for LCD display element. The transparent heat-resistant resin optical material is made of a copolymer containing a specific olefin residue unit and a specific N-phenyl-substituted maleimide residue unit and having a weight average molecular weight, as reduced into standard polystyrene, of from 5.times.10.sup.3 to 5.times.10.sup.6, the transparent heat-resistant resin optical material exhibiting negative birefringence; and a retardation film having a relationship of three-dimensional refractive indexes of nz.gtoreq.ny>nx, nz>ny.gtoreq.nx, or nz>nx.gtoreq.ny.
