Provided are an optical diffusion film composed of a single layer, for which the optical diffusion incident angle region can be effectively expanded, and even when the incident angle of incident light is varied within the optical diffusion incident angle region, changes in the optical diffusion characteristics can be effectively suppressed; and a method for manufacturing the optical diffusion film.Disclosed is an optical diffusion film having, inside the film, a single optical diffusion layer having a first internal structure and a second internal structure, each of which include a plurality of regions having a relatively high refractive index in a region having a relatively low refractive index, sequentially from the lower part along the film thickness direction, and the regions having a relatively high refractive index in the first internal structure have a bent section at an intermediate point along the film thickness direction.