A robot cleaner includes a cleaner body, a suction unit, and a cyclone unit. The cyclone unit has a first suction opening and a second suction opening for sucking air, and a first cyclone and a second cyclone for passing air therethrough, the air having dust filtered therefrom by a centrifugal force. A first guiding member and a second guiding member extend upwardly from the suction unit toward the cyclone unit with an inclination angle, the first guiding member for connection between the suction unit and the first suction opening, and the second guiding member for connection between the suction unit and the second suction opening. A dust box communicated with a dust discharge opening is provided at a front side of the cyclone unit so as to collect dust filtered by the cyclone unit. The dust box is partially or wholly accommodated between the first and second guiding members.