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