On both sides under a floor of an electric vehicle, side members are provided, each in a closed cross sectional shape. Collars and the like are provided in the side members. On a lower side of a lower wall of each of the side members, cross members which are fixed by using the collars or the like are provided. Between the side members on both sides, a main battery is provided and supported by the cross members. In the vicinity of a lower side of a doorway of the electric vehicle, a cutout part is formed such that a height of a portion of an upper wall of the side member is relatively lowered. On an upper surface of the cutout part, a reinforcing member is provided. A ramp passes through a space on an upper side of the cutout part.