PURPOSE: To provide a synthetic resin bumper beam of light weight and simple structure and having a sufficient impact energy absorbing effect by providing, in a U-shape cross sectional synthetic resin made bumper beam adapting a farther part from a car body as a bottom part thereof, obliquely crossing ribs for diagonally connecting an upper wall to a lower wall inside of the U-shape cross section.

CONSTITUTION: In a U-shape cross sectional synthetic resin made bumper beam 1 adapting a farther part from a car body as a bottom part thereof, obliquely crossing ribs 16, 18 for diagonally connecting an upper wall 12 to a lower wall 14 inside of the U-shape cross section are provided. In a vehicle bumper having this synthetic resin made bumper beam 1, since torsional rigidity is remarkably enhanced because of functions of oblique ribs 16, 18 inside the bumper beam 1, torsion is decreased not only in the case of an external impact being applied in the front direction or oblique direction but also in the case of a partial uneven impact being applied to an upper part or lower part of the bumper and a displacement quantity to the rear, namely, to a vehicle side is decreased. Furthermore, since reaction force of the bumper beam 1 itself is increased, a large quantity of impact energy can be absorbed with less deformation quantity.