To provide a method, by which a dielectric line can be manufactured efficiently with high reliability and accuracy.

In this method, an opening 19 is formed in the part of a photosensitive resist material 13 corresponding to wing sections 8 and 9 by patterning the material 13 by photolithography, after the material 13 is imparted to the external surface of the green mold 14, and a prescribed portion of the green mold 14 is removed by using the resist material 12 as a mask. Then a sintered body 22, having dielectric strips 6 and 7 and wing sections 8 and 9, is obtained by baking the obtained structure 21. While this method is adopted, the total reflectivity at the main photosensitive wavelength of the photosensitive resist material 13 is adjusted so as to be ≤15% in the interface between the green mold 14 and resist material 13.