To provide an optical film that gives phase retardation exhibiting reverse dispersibility with respect to wavelengths in the visible light region and exhibits low photoelasticity.

The optical film comprises a thermoplastic resin having a structural unit represented by formula (I). In the formula, R1 and R2 are each independently a hydrogen atom, a halogen atom, a 1-30C substituted or unsubstituted hydrocarbon group optionally bearing a linking group containing an oxygen atom, a nitrogen atom, a sulfur atom or a silicon atom, or a polar group.