The present invention relates to a structure for mounting a hook bracket formed of an aluminum alloy extrusion to a bumper reinforce having a hollow cross-section, and further reduces the weight of the hook bracket and the weight of the mount structure without deteriorating towing performance. The hook bracket has a cut that is formed in an extrusion cross-section (a cross-section perpendicular to the direction of extrusion) and extended from the rear end of a shaft portion into the hollow in the bumper reinforce. Further, an internally threaded hole is formed. The shaft portion of the hook bracket is penetrated through a hole formed in front and rear walls of the bumper reinforce and fillet-welded to the front and rear walls. The shaft portion is not fillet-welded to the rear wall at a position where the cut is formed.