The invention provides an optical filter, an optical device, and a projector, which make it possible to project a high-quality image by reducing or preventing color unevenness of the projected image. An optical filter is used in a projector that includes liquid crystal panels to modulate light beams from a light source (lamp) in accordance with image information to form optical images. The optical filter is disposed downstream from the liquid crystal panels in a light path, and includes a substrate and an optical conversion film. The optical conversion film is disposed on a light-incident surface of the substrate and includes two types of thin films having different refractive indices and being alternately stacked. The optical conversion film becomes continuously thinner from one end to the other end of the optical conversion film, so that it is inclined with respect to the substrate. Since the optical conversion film becomes continuously thinner, it is possible to project a high-quality image by reducing or preventing color unevenness of the projected image.