1. A location mark detecting method used by a robot cleaner, which includes an upwardly-looking camera capturing an area on which location marks are disposed, a control unit recognizing a current location based on an image captured by the camera and reference location marks stored in a storage, and a driving unit being driven in accordance with a signal of the control unit, in the location mark detecting method the control unit detecting the location marks from the image, the method comprising the steps of: obtaining from the image object marks to be compared with the stored reference location marks; determining whether the shapes of the object marks are identical to those of the stored reference location marks; determining whether the distance between the object marks is identical to the distance between the reference location marks if it is determined that the shapes are identical; determining whether a surrounding image of the object marks is identical to that of the reference location marks if it is determined that the distances are identical; and identifying the object marks as the location marks if it is determined that the surrounding images are identical.