Disclosed are an optical film having a graded refractive index and a method of manufacturing the same. The optical film includes one or more antireflection films composed of a mesoporous material having a plurality of pores of a uniform size, and the pores of the mesoporous material are filled with air or a filler having a refractive index different from that of the mesoporous material, and thus the volume ratio of mesoporous material to filler in the pores thereof is controlled, thereby obtaining a desired magnitude of effective refractive index and ensuring a refractive index distribution in which the refractive indexes sequentially change, resulting in high antireflection performance. The method of manufacturing the optical film may be conducted using a nanowire growing technique, thus making it easy to realize mass production.