OPTICAL FILTER

An optical filter including: a substrate; and a dielectric multilayer film laid on or above at least one major surface of the substrate as an outermost layer, in which: the dielectric multilayer film is a laminate including a low refractive index film and a high refractive index film laid on each other; the low refractive index film or the high refractive index film satisfies the spectral characteristics (i-1) and (i-2); the optical filter satisfies all of the spectral characteristics (ii-1) to (ii-3); and the optical filter has a nanoindentation hardness of 5.5 GPa or higher when a measurement load is 1 mN.