1. A road region detection method comprising: obtaining a set of first values and a set of second values representing distances related to one or more road regions from a map including the one or more road regions and an image corresponding to the map, respectively; and sequentially detecting plural sequentially adjacent road surfaces by iteratively detecting road surfaces based on corresponding sloped segments from a starting point where the first value and the second value are maximum, each road surface being formed by linear fitting plural reliable points, the plural reliable points being points that do not form a vertical line and, whose gray levels are greater than a threshold and first values are less than reliable points of previously detected road surfaces.