Abstract: The wheel-supported apparatus is used for climbing and descending stairs. The apparatus comprises a hollow main frame. A first carriage unit is located within the main frame and is slidably connected thereto. The first carriage unit is horizontally movable between a maximum front position and a maximum rear position by a first screw mechanism. A second carriage unit is slidably interconnected with the first carriage unit and is provided with a lower ground-engaging portion. The second carriage unit is movable vertically between a fully retracted position and a fully extended position by a second screw mechanism. The first and second screw mechanisms are operated in sequence for rising and backing the apparatus during climbing, and lowering and moving forward the apparatus during descent. Extendable supporting legs are used with a pair of rear caster wheels operatively connected under the main frame for periodically supporting the apparatus when climbing and descending the stairs.