A vehicle underbody structure capable of maintaining coupling between a brace and a floor frame against a load transmitted from the front side through the brace is provided, even without making a mechanical strength of a coupling portion between the brace and the floor frames particularly high. A brace is provided with a front-side coupling member and a rear-side coupling member, and the front-side coupling member and the rear-side coupling member are connected together by a load transmission section that is substantially M-shaped in plan view. The rear-side coupling member is connected to outside load transmission members of the load transmission section further to a left-right direction central side than a coupling portion of the rear-side coupling member to each floor frame. A load transmitted to the rear-side coupling member accordingly attempts to deform the rear-side coupling member about a rear end portion of the outside load transmission members.