[Problem] To provide an original film for manufacturing an optical film that has exceptional stretching performance, makes it possible to manufacture the optical film to be manufactured in a productive manner, and makes it possible to readily manufacture an optical film having both exceptional optical characteristics and exceptional hue, as well as a method for manufacturing an optical film in which the original film is used. [Solution] An original film for manufacturing an optical film, the original film containing a hydroxymethyl-group-containing vinyl alcohol polymer that contains a structural unit represented by the following formula (1) and a vinyl alcohol unit; and a method for manufacturing an optical film, the method having a step for performing uniaxial stretching using the original film for manufacturing an optical film.