1. A method for detecting straight line information, comprising steps of: inputting an image with extracted edge (step A) designating pixels of the image into block-wise units each comprising a predetermined number of pixels (step B); calculating votes of representative pixels per designated block (step C); calculating votes of rest pixels per block, using the votes of the representative pixels per block (step D); counting accumulated frequencies per vote, using the votes calculated at steps (C) and (D) (step E); and detecting straight line information based on the accumulated frequency information that exceeds a threshold (step F).