An underrun prevention member for a vehicle bumper beam including a substantially vertical outer side wall faced an area outside the vehicle and a horizontal wall provided so as to be extended substantially horizontally from an end of the outer side wall in a top-bottom direction toward an inside of the vehicle, disposed at a front portion or a rear portion of the vehicle so as to be extended substantially horizontally in a vehicle widthwise direction, and integrally fixed to the bumper beam so as to protrude in the top-bottom direction beyond the horizontal wall to prevent an underrun of the bumper beam under an object outside the vehicle or the object outside the vehicle under the bumper beam.