PURPOSE: To continuously and integrally extrude a molding of a full length while forming solid parts in a part of the molding having a hollow cross section.

CONSTITUTION: While decorative parts 11 forming hollow parts 1B serve as apparently solid parts by unnecessary bodies 12a, a molding material is once extruded to its full length so as to have the same cross sectional shape. The unnecessary bodies 12a are removed from the obtained molding material in a separation process. In this manner, a continuous and integral molding 1 is provided with the decorative parts 11 forming the hollow parts IB and reinforcing ribs 12 forming solid parts 1A.