An optical device includes first and second laminated films of alternate layers of optical thin films of high refractivity material and low refractivity material, and having an optical film thicknesses of "a" and "b" respectively; wherein b>a, and an optical plate on which the first laminated film and the second laminated film are formed in sequence from at least one primary surface of the optical plate, wherein a third laminated film comprised of a lamination of optical thin films of high refractivity material and low refractivity material and having an optical film thickness "c" is interposed between the first laminated film and the second laminated film, wherein b>c>a. As a result, an optical device which has spectral characteristics where ripple in the opaque zone which blocks infrared light is suppressed, can be obtained.