A bow-formed bumper beam for a vehicle has a hat profile with a central flange (11), two webs (12, 13), and side flanges (14, 15). The beam has fastening portions (20, 21) at its sides where the side flanges form fastening areas (30-33) for fastening the beam to the vehicle with the central flange facing outwards. In the area between the fastening areas, the side flanges have bent edges (26, 27) and in association with the beginning of the bent edges, they have transverse dents (29). These dents will easily be flattened out when the beam is bent in a collision so that the local tension in these sensitive areas is reduced. Thereby, the risk of cracking is reduced.