A vehicle includes: an image acquisition means (4) which acquires a road image via an imaging means (3); an edge extraction means (5) which extracts edge points from the acquired image; a line search means (6) which searches the extracted edge points for line components; an evaluation value calculation means (7) which calculates an evaluation value indicating the degree that each line component approximates a linear lane mark on the road for the line components searched for; a lane mark candidate selection means (8) which selects line components each having an evaluation value greater than a predetermined threshold value as candidates for a line component corresponding to the lane mark from the line components searched for; and a lane mark detection means (9) which detects the lane mark by determining the line component corresponding to the lane mark from the selected candidates for the line component. This allows the detection accuracy to be increased by preventing an object other than a lane mark on the road from being incorrectly detected as a linear lane mark such as a white line when detecting a linear lane mark such as a white line from the road image.