Of side wall portions (60a, 60b) of a tubular body portion (52) mainly constituting an impact absorbing member (50), a wider side wall portion (60a) on the vehicle inner side is provided with a projecting rib (70) projects outward in the direction perpendicular to the axis of the body portion. The projecting rib (70) extends from an axial end (52a) adjacent to a mounting plate (54) and parallel to the axial direction of the body portion. Therefore, even when an impact load is applied to the impact absorbing member (50) in an oblique direction with respect to the vehicle to generate a moment load, the existence of the projecting rib (70) prevents the impact absorbing member from falling down laterally. Accordingly, excellent impact-absorbing properties are stably obtained. The projecting rib (70) is formed not to reach the load input side, i.e., the axial end (52b) adjacent to a mounting plate (56), where collapse starts. Therefore, no load increase occurs in a crash initial stage to well maintain impact-energy-absorbing properties.