An image processor for an automotive vehicle includes: an imaging element for capturing an image of a road; a traffic lane line detection element for detecting a position of a traffic lane line by determining an edge of the traffic lane line; a distance distribution calculation element for calculating a distance distribution of an edge intensity corresponding to a distance to the traffic lane line from the imaging element; and a detection reliability calculation element for calculating a degree of reliability of detection of the traffic lane line on the basis of the distance distribution of the edge intensity of the traffic lane line.