In a self-traveling cleaner of the present invention, a cleaning mechanism includes a brush mechanism rotatable along a floor surface and a driving mechanism for rotatingly driving the brush mechanism. The brush mechanism includes a rotation axis extending perpendicular to the floor surface, one arm projecting laterally from a lower end of the rotation axis, and a brush planted on the arm. The rotation axis is provided within a reverse side of the main body, and the arm has a rotation angle range in which the arm projects outwardly from an outer periphery of the main body and a rotation angle range in which the arm is contained within the outer periphery of the main body.