Method of manufacturing a transmission line including the steps : - forming an element with at least one longitudinal groove on a surface of said element, said longitudinal groove being defined by two opposite wall portions in the element and having a longitudinal opening adjacent to said surface, and - locating a conductor line in said at least one longitudinal groove. The method is distinguished by the steps: - forming the conductor line from a metal strip upon punching the same from a sheet of metal, - attaching the metal strip to at least one holding device, and - mounting said at least one holding device, with the attached metal strip, on said element, so as to locate said metal strip in said longitudinal groove at a distance from said opposite wall portions of said element. The invention also concerns a transmission line manufactured in accordance with said method.