PURPOSE: To provide the band-pass filter which is composed of.dielectric multilayered films, has a desired pass-band width, has less dependency on polarized light and is good in rising characteristic.

CONSTITUTION: This band-pass filter is constituted by alternately laminating high-refractive index dielectric films and 'low-refractive index dielectric films on both sides of a cavity layer and its central wavelength of the pass band is λ0. The optical film thicknesses of the respective high-refractive index dielectric films and the low-refractive index dielectric film are λ0/4 and the optical film thickness of the cavity layer of integer times λ0/2 is made large within a range larger than 0 and smaller than λ0/2.