An autonomous traveling cleaner for traveling autonomously on a target surface and cleaning the target surface, the autonomous traveling cleaner comprising: a driving force transmitter configured to transmit, to the target surface, a moving force of the autonomous traveling cleaner in a traveling direction with a body of the autonomous traveling cleaner in a traveling posture; a suction nozzle including a first rotary brush configured to sweep the target surface, the suction nozzle being configured to suck first suction matter collected by the first rotary brush; wherein the autonomous traveling cleaner has an elongated profile having a larger dimension in the traveling direction than a width direction orthogonal to the traveling direction; characterized in that the autonomous cleaner further comprises: an extension nozzle extendable laterally with respect to the traveling direction and including a second rotary brush configured to sweep the target surface, the extension nozzle being configured to suck second suction matter collected by the second rotary brush; and a collection box including an inlet (161, 168), the collection box being configured to collect, through the inlet (161, 168), the first suction matter sucked by the suction nozzle and the second suction matter sucked by the extension nozzle, the extension nozzle is switchable between a first posture and a second posture, the extension nozzle in the first posture is positioned without laterally protruding from the autonomous traveling cleaner and has an airflow path being blocked from the extension nozzle to the collection box, the extension nozzle in the second posture is positioned to laterally protrude from the autonomous traveling cleaner and has an airflow path forming from the extension nozzle to the collection box, the extension nozzle in the second posture is pivotable in a direction opposite to the traveling direction, and the extension nozzle in the second posture has a protruding end in the width direction to be aligned with an end of a turning range of the autonomous traveling cleaner in the width direction, when the autonomous traveling cleaner is viewed in the traveling direction. a driving force transmitter configured to transmit, to the target surface, a moving force of the autonomous traveling cleaner in a traveling direction with a body of the autonomous traveling cleaner in a traveling posture; a suction nozzle including a first rotary brush configured to sweep the target surface, the suction nozzle being configured to suck first suction matter collected by the first rotary brush; wherein the autonomous traveling cleaner has an elongated profile having a larger dimension in the traveling direction than a width direction orthogonal to the traveling direction; characterized in that the autonomous cleaner further comprises: an extension nozzle extendable laterally with respect to the traveling direction and including a second rotary brush configured to sweep the target surface, the extension nozzle being configured to suck second suction matter collected by the second rotary brush; and a collection box including an inlet (161, 168), the collection box being configured to collect, through the inlet (161, 168), the first suction matter sucked by the suction nozzle and the second suction matter sucked by the extension nozzle, the extension nozzle is switchable between a first posture and a second posture, the extension nozzle in the first posture is positioned without laterally protruding from the autonomous traveling cleaner and has an airflow path being blocked from the extension nozzle to the collection box, the extension nozzle in the second posture is positioned to laterally protrude from the autonomous traveling cleaner and has an airflow path forming from the extension nozzle to the collection box, the extension nozzle in the second posture is pivotable in a direction opposite to the traveling direction, and the extension nozzle in the second posture has a protruding end in the width direction to be aligned with an end of a turning range of the autonomous traveling cleaner in the width direction, when the autonomous traveling cleaner is viewed in the traveling direction.