1. A method for localizing a mobile robot using arbitrarily shaped (AS) ceiling features, comprising: a device providing step of providing a mobile robot device which is localized using the arbitrarily shaped ceiling features and includes an image input unit, an encoder sensing unit, an arithmetic unit, a control unit, a storage unit, and a driving unit; a feature extraction step of extracting features which include an arbitrarily shaped feature from a contour extracted from image information inputted through the image input unit; and a localization step of localizing the mobile robot device using the extracted features, wherein a descriptor indicating the characteristics of the arbitrarily shaped feature is assigned in the feature extraction step, wherein the feature extraction step comprises: a region-of-interest (ROI) extraction step of detecting and labeling the contour from the image information, and extracting a region of interest (ROI); an ROI descriptor creation step of assigning a descriptor indicating the characteristics of the region of interest to the region of interest; and an ROI robustness confirmation step of confirming whether or not the region of interest is set as a feature used in the localization step based on the descriptor of the region of interest and a preset reference stored in the storage unit, wherein the ROI robustness confirmation step comprises: an ROI similarity calculation step of calculating a similarity defining a resemblance between regions of interest in the current image; an ROI uniqueness calculation step of calculating a region-of-interest (ROI) uniqueness by assigning a weighting factor to a similarity between other regions of interest adjacent to the region of interest in the current image; a uniqueness determination step of comparing the calculated ROI uniqueness with a preset uniqueness stored in the storage unit, and determining whether or not the calculated ROI uniqueness has stability as a feature; and an ROI robustness determination step of confirming whether or not the ROI uniqueness is used as a feature of the region of interest depending on a result of determination in the uniqueness determination step.