To improve impact absorption capability at the early stage of deformation and to enable simplification of the production process by forming a plastic deformation inducing portions with different cross sectional shapes on a part of the extrusion directions by variable section extrusion molding.

Recess portions 16 are formed on outer faces of a pair of parallel side walls as a plastic deformation induction portion in the vertical direction thereof. They are made by an operation to make a supplementary dies to stick out to the inside of a dies hole of the extrusion dies while continuing extrusion operation at the time of extrusion molding using the extrusion dice. The recess portions 16 are thin, and differ in their sectional shapes in relation to the other portion of an energy absorber 10 in the extrusion direction. For instance, when an impact is applied to its longitudinal directions, stress is concentrated on both of the recess portions 16. Then a plastic deformation is induced after some elastic deformation, thereby the entire portion is plastic deformed. This allows quick shift to the plastic deformation at the early stage of the deformation, enabling effective absorption of the impact energy. Further, molding to be conducted under the series of molding process simplifies the molding process.