This paper proposes a method which uses the extended edge analysis to supplement the inaccurate edge information for better vehicle detection during vehicle detection.The extended edge analysis method detects two vertical edge items,which are the borderlines of both sides of the vehicle,by extending the horizontal edges obtained inaccurately due to the illumination or noise existing on the image.The proposed method extracts the horizontal edges with the method of merging edges by using the horizontal edge information inside the Region of Interest(ROI),which is set up on the pre-processing step.The bottom line is determined by detecting the shadow regions of the vehicle from the extracted horizontal edge one.The general width of the vehicle detecting and the extended edge analyzing methods are carried out side by side on the bottom line of the vehicle to determine width of the vehicle.Finally,the final vehicle is detected through the verification step.On the road image with complicate background,the vehicle detecting method based on the extended edge analysis is more efficient than the existing vehicle detecting method which uses the edge information.The excellence of the proposed vehicle detecting method is confirmed by carrying out the vehicle detecting experiment on the complicate road image. This paper proposes a method which supplement the inaccurate edge information for better vehicle detection during vehicle detection. The extended edge analysis method detects two vertical edge items, which are the borderlines of both sides of the vehicle, by extending the horizontal edges obtained inaccurately due to the illumination or noise existing on the image the proposed method extracts the horizontal edges with the method of merging edges by using the horizontal edge information inside the Region of Interest (ROI), which is set up on the pre The processing of the bottom line of the vehicle is carried out from the bottom line of the vehicle to determine width of the vehicle .Finally, the final vehicle is detected through the verification step. On the road image with complicate b ackground, the vehicle detecting method based on the extended edge analysis is more efficient than the existing vehicle detecting method which uses the edge information. excellence in the proposed vehicle detecting method is confirmed by carrying out the vehicle detecting experiment on the complicate road image.