A robot cleaner includes: a suction unit installed at a cleaner body, for sucking dirt on a floor; a driving unit for moving the cleaner body; a sensing unit mounted at the cleaner body, for sensing a depressed portion and a stepped portion such as a doorsill of a floor; and a control unit receiving a signal of the sensing unit, for controlling the driving unit to allow the cleaner body to avoid the depressed portion and the stepped portion, thereby correctly sensing the depressed portion or the stepped portion of the floor and avoiding such a portion. Accordingly, the cleaning operation is stably carried out.