A vehicle includes vehicle body-side steps having a plurality of abutment surfaces on which seat-side protrusions abut from above. Each abutment surface has a height different from each other, with the seat being adjustable in height by selectively abutting the seat-side protrusions on the abutment surfaces. A rider's seat has a covering portion formed at a front portion thereof and extending substantially in parallel with an inclined upper surface of a fuel tank. When abutment positions of the seat-side protrusions are changed from either first ones of the abutment surfaces to second ones, the covering portion changes a position thereof so as to slide substantially in parallel with the inclined upper surface of the fuel tank.