1. A lane-marker recognition system installed in a vehicle, comprising: an image pickup unit that repeatedly picks up a frame image of a target region including a road ahead of the vehicle; an edge extracting unit that extracts an edge of a lane marker formed on the road from each of the frame images picked-up by the image pickup unit; a history creating unit that creates a history of the edges of the lane marker for the respective frame images by storing the edges of the lane marker for the respective frame images; a pitch detecting unit that detects pitch of the vehicle, the history creating unit being configured to omit, as a target edge, an edge from the history of the edges for the respective frame images, the target edge to be omitted being extracted from one of the frame images, the one of the frame images being picked up by the image pickup unit with the pitch being detected by the pitch detecting unit; and a lane-marker recognizing unit that recognizes a region of the lane marker based on the history of the edges of the lane marker.