1. A system for recognizing a traffic lane marking line for a vehicle comprising image photographing means for photographing a range including a road surface in a direction of travel of the vehicle; traffic lane marking line recognizing means configured to be capable of recognizing at least a traffic lane marking line in broken line on the road surface in a photographed image photographed by the image photographing means; image compositing means for compositing a plurality of images photographed at different time points by the image photographing means to elongate the traffic lane marking line in the photographed images; brightness detecting means for detecting brightness of the plurality of images photographed by the image photographing means; and brightness correcting means for correcting the brightness, taking one image among the plurality of images as a reference, such that the brightness of the plurality of images are equal to each other; and the image compositing means composites the plurality of images after the brightness has been corrected by the brightness correcting means.