A cover for a fuel tank includes a flange unit configured to close an opening of the fuel tank and a joint member movably coupled to the flange unit. The joint member is configured to move in an upward/downward direction relative to the flange unit. Two side tubular portions extend from the flange unit in the upward/downward direction and are positioned side-by-side. Column portions extend in the upward/downward direction from the joint member. The column portions are moveably disposed in the side tubular portions. The column portions are configured to move in the upward/downward direction relative to the side tubular portions. The side tubular portions are connected to each other via a rear side wall and a front side wall of a center tubular portion disposed between the side tubular portions.