There is provided a novel, improved optical body, the micro concave-convex structure of which can be protected without the use of a protective film, a film adhesive body, and a method for manufacturing an optical body, the optical body including: an optical film, on one surface of which is formed a first micro concave-convex structure in which an average cycle of concavities and convexities is less than or equal to a visible light wavelength; and a master film that covers the first micro concave-convex structure. The master film is provided with a second micro concave-convex structure formed on a surface that faces the first micro concave-convex structure, the second micro concave-convex structure is made of a cured curing resin, and has a reverse shape of the first micro concave-convex structure, and the optical film and the master film are separable from each other.