A method of detecting a biometric region, the method including receiving an input image; setting a plurality of regions of interest (ROI) corresponding to a plurality classifiers, respectively, the plurality of classifiers corresponding to a plurality of multi-stages, respectively, the plurality of ROIs having different sizes with respect to each other, each ROI of the plurality of ROIs including a biometric region of the input image; calculating a plurality of similarity values for the plurality of classifiers, respectively, based on the ROIs corresponding to the plurality of classifiers from among the plurality of ROIs; and detecting a first biometric region for a user authentication based on at least one of the plurality of similarity values.