An automoblile bumper comprising a blow-molded hollow body (5) of synthetic resin located between a surface skin (1) and a reinforcement (2), the hollow body (5) having recesses (7) formed by longitudinally extending ribs (6a) and (6a) on either the front or rear side, or on both sides, whereby the bumper uniformly absorbs impact energy when it is hit and thus reduces shocks transmitted to a car body.