An edge image generating unit 12 generates an edge image, into which edge points whose variation in luminance relative to a surrounding portion is equal to or more than a predetermined value have been extracted, from an image captured by a camera 2. A candidate image portion extracting unit 13 extracts a candidate image portion, which is a candidate for an image portion of a lane mark, from the edge image. A lane mark recognizing unit 14 detects a lane mark candidate on the basis of the candidate image portion and, in the case of having detected a plurality of lane mark candidates 51b to 54b and 61b to 63b adjacent to each other, compares the luminance of a corresponding area in the captured image for each of the lane mark candidates and recognizes the lane mark candidate 51b to 54b having the maximum luminance value as a lane mark.