Abstract: An image pickup unit (2) mounted on a vehicle shoots an image in front thereof to attain image information. An edge pixel extraction section (40202 to 40206) scans the obtained image information for each line and then checks boundaries between a particular color and the other colors to extract pixels having the particular color as edge pixels. Moreover, a candidate line extraction section (40208 to 40212) references position coordinates of the extracted edge pixels such that assuming the edge pixels to be classified to configure straight lines, the edge pixels are coupled with each other to configure straight lines according to the classification so as to obtain the straight lines as candidate lines.Thereafter, a line selection section (40212) selects a left line and a right line in front of the vehicle from the plural candidate lines, thereby attaining the left and right lines.