A robot cleaner comprises a main body having a suction port at a bottom surface thereof, a pair of wheel assemblies disposed at both sides of the main body, and configured to move the main body, a dust box mounted to contact the bottom surface of the main body, and configured to collect dust sucked through the suction port, a filter unit configured to filter air discharged from the dust box, a suction fan configured to form a suction pressure on a suction channel defined by the suction port, the dust box and the filter unit, and a battery disposed at a side of the dust box.