When a sealing portion at an end portion of an extruded weatherstrip is cut out by a fixed length and a main body and a lip are set on a metal mold for die forming, concave portions are formed on a lower surface and side surface of the main body to be set on the metal mold, and are latched, respectively with convex portions of the metal mold to restrict movement. Thus a problem in external appearance caused by movement or bending of a part of the main body including the lip due to a molding pressure is eliminated.