An adhesive agent is uniformly applied to a back surface of a window pane, the application made to an area where a covering member is planned to be adhered and to an area where a positioning fixture and a holding portion are planned to be adhered, the application is also made continuously such that adhesive agent layers of both planned adhesion areas being continuous with an adhesive agent continuous area in between. After that, the window pane and the positioning fixture are set in an injection mold and a polymer material is injected in the mold. This results that the covering member and the holding portion are formed into a shape where they are connected by a connection portion for material flow, which connection portion is formed at a position other than the adhesive agent continuous area. The forming results that the covering member and the holding portion are adhered and fixed to the back surface of the window pane with the adhesive agent layers in between. After the forming process above, the connection portion for material flow is removed.