Provided is a robot cleaner including a main body including a suction portion disposed thereon, main wheels for moving the main body, and a side brush assembly disposed on the main body and rotating with a rotation shaft perpendicular to a rotation shaft of the main wheels, the side brush assembly includes a housing for forming an exterior of the side brush assembly, a first force transmitter disposed in the housing and rotating by receiving a driving force, a belt connected to the first force transmitter, a second force transmitter connected to the first force transmitter by the belt to receive a rotational force of the first force transmitter, and a side brush coupled to the second force transmitter.