PURPOSE: To prevent the occurrence of granular protrusions, and enable the surface to be smoothed by heating the extrusion molding of a rigid rubber material from the outside so as to vulcanize only the surface of the extrusion molding, and thereafter subjecting to high frequency heating in order to temperature raise the inside of the extrusion molding, and then effecting heat-hot insulation from the outside thereof for completing vulcanization.

CONSTITUTION: An extrusion molding wherein a rigid rubber material is continuously extrusion-molded into the cross-sectional shape of a glass run 1 is passed through a hot air furnace and an infrared oven to heat the extrusion molding from the outside thereof. In this heating process, only the surface layer of the extrusion molding is vulcanized in adjusting the heat temperature and time. Subsequently, it is passed through a high frequency unit for temperature-raising the inside of the extrusion molding rapidly uniformly. Then it is passed through heating means such as a hot air furnace, infrared oven and the like for maintaining the extrusion molding at high temperature and the vulcanization is completed. After this, it is passed through a cooling bath to be cooled and then cut into a predetermined length by means of a severing machine. In this way, a glass run can be obtained which is smooth in its surface and therefore excellent in its appearance.