A robot cleaner 1 includes a main body 2 travelling along a floor surface and removing foreign substances in a cleaning travel mode, a sensor unit 3, 110 sensing obstacles around the main body 2, brush units 10, 20, 110, 130 sweeping foreign substances on a floor surface through rotation, and a controller 150 reducing the travelling velocity of the main body 2 and causing the main body 2 to approach a front obstacle, if an area where a plurality of obstacles contacts each other is sensed by the sensor unit 3, 110.