1. An obstacle recognition system for a vehicle, comprising: an image photographing unit comprised in the vehicle, and configured to generate a single source image which is obtained by photographing a front view or a rear view while the vehicle is driving; an edge image generation unit configured to receive the source image, and generate an edge image which represents an object comprised in the source image as an edge line; a region of interest (ROI) detection unit configured to divide the edge image into a predetermined number of regions according to a speed value of the vehicle, calculate a total sum of edge component values of the edge line for each region, compare the total sum of edge component values of each of the regions and a predetermined threshold value for each of the regions, and detect a region from the number of regions as an ROI that provides information of the object in front of the vehicle on the basis of the compared result for each of the regions; and an image analysis unit configured to scan the detected ROI by block units having a certain size to analyze whether an obstacle exists in the detected ROI, wherein the ROI detection unit comprises: an image divider configured to receive the speed value of the vehicle from a vehicle system, and divide an entire region of the edge image into a predetermined number of regions according to the received speed value of the vehicle; an edge value collector configured to calculate a total sum of edge component values of an edge line which is comprised in each of the regions, and collect the calculated total sum of edge component values of each of the regions; and a comparator configured to compare the total sum of edge component values of the edge line of each of the regions and the predetermined threshold value for each region, and detect a region, in which the total sum of edge component values is greater than the threshold value, as the ROI from among the plurality of regions, wherein the image analysis unit is configured to scan only the detected ROI without scanning any other region of the plurality of regions in order to reduce a processing time of the scanning, wherein when an entire size of the edge image is i*j, i being the number of pixels in a horizontal direction, and j being the number of pixels in a vertical direction, a size of each of the divided regions is i*(j/n), n being a natural number from two to six, wherein as a speed of the vehicle increases, the n increases, in order to decrease a detection error occurring in an operation of detecting the ROI when the entire region of the edge image is divided into equal portions irrespective of a vehicle speed.