There are provided an optical filter excellent in weather resistance and a method for manufacturing an optical filter. The optical filter of the present invention includes a transparent substrate, and an optical multilayer film provided on a surface of the transparent substrate. In the optical multilayer film, a low-refractive index film containing silicon oxide (SiO2) and a high-refractive index film higher in refractive index than the low-refractive index film are alternately stacked. A density of a portion of the low-refractive index film close to an interface between the low-refractive index film and the high-refractive index film is lower than a density of a portion of the low-refractive index film other than the portion close to the interface.