A motorcycle with an increased rigidity portion for supporting a storage box. A body frame includes a main frame extending rearward and obliquely downward from a head pipe. Left and right seat rails are connected to the rear portion of the main frame and extend rearward and obliquely upward. Left and right backstays extend between and are connected to the left and right seat rails and the rear end of the main frame. A storage box is disposed such that its bottom is positioned above a connection part of the main frame and the backstays, and the storage box has front and rear attachment parts secured to the seat rails. The front and rear attachment parts are separately disposed, respectively, forward and rearward of a vertical line that passes through the connection part.