Traffic lane boundary line extraction apparatus and method of extracting traffic lane boundary line

A traffic lane boundary line extraction apparatus includes: an image-data-acquiring-unit configured to acquire vehicle outside image data captured by a travelling vehicle; a candidate-area-detection-unit configured to detect a candidate area of a traffic lane boundary line from a road surface part of the vehicle outside image data; a road-surface-area-setting-unit configured to set a road surface area corresponding to the candidate area in the road surface part of the vehicle outside image data for each of the candidate area; a luminance-calculation-unit configured to calculate a representative luminance of the candidate area, and a representative luminance of the road surface area; and if a difference between the representative luminance of the candidate area and the representative luminance of the road surface area is greater than a predetermined threshold value, a candidate area evaluation unit configured to evaluate that the candidate area is suitable for the traffic lane boundary line.