A reinforcing member for vehicles comprises a pair of fixed parts fastened on spaced-apart portions of a vehicle body, and a bar body for connecting the respective fixed parts. A rotation allowing mechanism is provided on at least one of the fixed parts in order to allow the bar body to rotate with respect to the vehicle body. Therefore, the respective two portions of the vehicle body, on which the fixed parts are fastened respectively, are allowed to have angle variations to each other without changing the space between the two portions of the vehicle body. Consequently, the rigidity of the entire vehicle body can be improved without the degradation in the drivability and the ride comfortableness of the vehicle.