Free space detection is very important for vehicle navigation and safe driving. 3-D line segment reconstruction of a street is important for the free space detection because a street-view includes many line segments. For the free space detection, we propose a method for reconstructing 3-D line segments in a streetscape using a monocular in-vehicle camera. The 3-D reconstruction of the line segments is achieved by using each three images from an image sequence. Once accurate camera poses of these images are obtained, one of the remaining crucial problems is to match the line segments between the images correctly. A strategy for finding correspondence of the line segments is as follows: First, the correspondences of line segment candidates are searched by using a two-view constraint. However, the two-view constraint has difficulty on determining an unique correspondence geometrically. Therefore, the candidates of the line segment correspondences are reduced using a three-view constraint. In order to improve the accuracy, the proposed method exploits a color feature of the line segment and a preliminary knowledge of the vehicle motion. Finally, the line segments are reconstructed using the correspondences. From an experimental result, we confirmed the effectiveness of the proposed method. Application to the free space detection demonstrated the usefulness of the reconstructed line segments.