The method includes receiving an image of a user's eye region, selecting pixels included in a central region of the image, calculating an average value of brightness values of a plurality of adjacent pixels among the pixels included in the central region, converting the plurality of adjacent pixels into one pixel having the average value as a brightness value, comparing the brightness values of the converted pixels with a critical value to binarize the converted pixels, so as to create a binarized image, detecting a row including a pixel located at an uppermost end of pixels corresponding to a pupil, from the binarized image and correcting the position of the central region such that the pupil is located at the center of the image, based on position information of the row including the pixel located at the uppermost end of the pixels corresponding to the pupil.
