A structure for sufficiently spacing a steering handle from a top bridge, thereby greatly improving design flexibility. A relief portion for allowing the deformation of a washer is formed to overlap a second contact surface and adjacent to a first contact surface as viewed in the axial direction of each bolt member. The first contact surface is located so as not to overlap the second contact surface as viewed in the axial direction of each bolt member. Therefore, a bending force acts on the washer to allow the deformation of the washer. That is, the washer can exhibit a spring function to relax the effect of the bending force. As a result, the steering handle can be sufficiently spaced from the top bridge to thereby greatly improve design flexibility.