There is provided a new and improved optical body, a new and improved method for manufacturing an optical body, and a new and improved light emitting device that can emit light derived from a light source in more various manners. The optical body includes: a base material; and a first concave-convex structure that is formed on at least one surface of the base material and that extracts internally propagating light that is injected into an inside of the base material from a side surface of the base material. An average period of concavity and convexity of the first concave-convex structure is more than or equal to a minimum value of a visible light wavelength band and less than or equal to 10 μm.