To enhance the energy absorbing efficiency by providing an inside strength member having a closed sectional form within an outside strength member, and providing a guide member for receiving the other end of the inside strength member and specifying the mode of extrusion deformation of the other end on the other end of the outside strength member.

One-side ends of an outside strength member 2 and an inside strength member 3 are mounted on a first support member, and the other end 2b of the outside strength member 2 and a guide member 4 are mounted on a second support member 6. A space S is provided between the other end 3b of the inside strength member 3 and the guide member 4. When a load is received, the outside strength member 2 is deformed in bellows with a horizontal beat as a start. An initial distortion part formed on the other end 3b of the inside strength member is collided with the guide member 4, and the other end 3b is plastically deformed in the extruding direction. Thus, the energy of the load is surely absorbed by a short stroke.