A traffic lane marking line recognition system for a vehicle includes an image compositing device which composites images photographed at different time points by a camera to elongate a traffic lane marking line such as a white line in the photographed image, the brightness of the photographed images is detected, the brightness is corrected, taking one image among the plurality of images as a reference, such that the brightness of the plurality of images is equal to each other, and the plurality of images are composited after the brightness has been corrected. By making the brightness of the images to be composited equal to each other, it becomes possible to recognize the traffic lane marking line accurately and unerringly.