In a vehicle frame structure, an upper edge of a frame member is fixed to a lower face of a substantially flat panel, and a bottom wall of an upper stiffener fixed to an inner face of an upper part of a curved portion of the frame member and a bottom wall of a lower stiffener fixed to an outer face of a lower part of a region between two inflection points of the curved portion are arranged in an X shape relative to a top point of the curved portion. Therefore, when a compressive load in the longitudinal direction acts on the frame member, the curved portion of the frame member is effectively prevented from bending by counterbalancing the upward load acting on the lower stiffener bottom wall with the downward load acting on the upper stiffener bottom wall. Moreover, the upper stiffener and the lower stiffener are U-shaped cross-section members that can be formed by bent sheet metal, and thereby minimize any increase in weight due to installation of the stiffeners.
