STRUCTURE FOR LOWER PORTION OF VEHICLE

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 (60) is provided with a front-side coupling member (62) and a rear-side coupling member (92), and the front-side coupling member (62) and the rear-side coupling member (92) are connected together by a load transmission section (100) that is substantially M-shaped in plan view. The rear-side coupling member (92) is connected to outside load transmission members (102) of the load transmission section (100) further to a left-right direction central side than a coupling portion of the rear-side coupling member (92) to each floor frame (30). A load transmitted to the rear-side coupling member (92) accordingly attempts to deform the rear-side coupling member (92) about a rear end portion of the outside load transmission members (102), thereby reducing the load acting to fracture the coupling portion between the rear-side coupling member (92) and the floor frames (30).