Abstract: A robot cleaner is mainly comprised of a base case whose upper portion is equipped with a driving part for running and a suction part for removing dust or dirt; and a top case covering on top of said base case, wherein said base case is formed at lower portion thereof with an inside vertical wall protruding so as to surround dust suction aperture, and with an outside vertical wall external to said inside vertical wall so that a hollow part may be formed in-between surrounding said inside vertical wall; and an auxiliary suction wall is installed between said inside vertical wall and outside vertical wall in such a manner that said auxiliary suction wall is movable by force of spring external to said inside vertical wall between a No. 1 position locating toward floor (F) and a No. 2 position locating withdrawn from said No. 1 position opposite to floor (F), said auxiliary suction wall being positioned toward floor (F) when no external forces are applied.