An optical film includes at the least one retardation film and at least one isotropic layer made of an isotropic material, wherein the difference in average refractive index between the retardation film and the isotropic layer is at least 0.1 or more. Also, the method of adjusting wavelength dispersion characteristics of an optical film includes: stacking an isotropic layer onto a retardation film. A method for preparing optical film having a variety of wavelength dispersion characteristics by the simple method of coating the retardation film with the isotropic layer.