A robot cleaner including a suction hole to suction dust, a blower to generate a suction force to suction the dust, a dust collector to receive the dust suctioned by said suction force through the suction hole, and a rotating brush to sweep up and collect the dust into the dust collector through the suction hole by a drive force of the rotating brush. The dust collector includes a backflow preventing member movable between an open position and a closed position. The backflow preventing member is pivotably rotatable in an air suction direction by the suction force of the blower to the open position and is adapted to return to the closed position to prevent the dust in the dust collector from being discharged through the suction hole upon stoppage of the blower.