Abstract: An optical device which can be fabricated without any axial alignment by optical measurement and can therefore be produced at a remarkably decreased cost, and which is composed of an optical waveguide part (1) obtained by perpendicularly cutting an optically-transparent polymer film having a glass substrate attached thereto and having a refractive index distribution formed, in a predetermined position measured from the position of the refractive index distribution as a reference, and a holder part (2) for holding the optical waveguide part (1) in a predetermined position, the holder part (2) having a horizontal guide surface (2H) and a vertical guide surface (2V), the optical waveguide part (1) having a glass substrate surface or a polymer film surface coherently attached to the horizontal guide surface (2H) of the holder part (2), and the optical waveguide part (1) having a perpendicularly cut surface coherently attached to the vertical guide surface (2V) of the holder part (2).