PURPOSE: To prevent stock material from overflowing when it is foamed and to facilitate the finishing of a headrest, by opening a projection to form French window type lids, introducing a core with styas into the covering, and pouring a foamable mateial into the covering.

CONSTITUTION: By a rotary molding machine, the projection 21 is formed on the headrest body to project from it to have a box-shape having a rectangular bottom, and the projection 21 is cut off by suitable means so that the French window type lids 22 are left. The lids are opened, the core 24 attached with stays 23 is introduced into the body, and after a foamable material 25 is filled, the headrest body with the lids closed is set in foaming molds to foam the material 25 to obtain a molded headrest. Thus, after the foaming, the foamable material would not overflow, and the material introducing inlet can be closed readily in a neatly finished condition.