The present invention discloses a lane detecting apparatus mounted on a vehicle including a camera for obtaining an image of a lane marking drawn on a road, a candidate line selecting part for selecting one or more candidate lines having edge information no less than an edge threshold from the image obtained by the camera, and a car pool lane determining part for determining whether the difference in the number of the candidate lines between the left side of the vehicle and the right side of the vehicle is no less than a predetermined value. When the difference is no less than the predetermined value, the lane detecting apparatus transfers to a car pool lane detection mode in which the candidate line selecting part detects the one or more candidate lines in accordance with a threshold that is less than the edge threshold.