Embodiments of the disclosure relate to a robot cleaner and a controlling method thereof, and more particularly, to a robot cleaner and a traveling algorithm of a robot cleaner having an improved structure. A robot cleaner of the disclosure includes a brush unit having a suction flow path, a body unit configured to have a driving device, and be coupled to the brush unit to be rotatable with respect to the brush unit and a redirection device configured to rotate the body unit relative to the brush unit, and the redirection device includes a rotation guide extending along an inner circumferential surface of the brush unit, a rotation driving source disposed in the body unit and generating power, and a power transmission member which moves along the rotation guide by the power transmitted from the rotation driving source and rotates the body unit with respect to the brush unit.