1. A vehicle free parking space detection apparatus comprising: a feature points tracker for tracking feature points by receiving input images from an image captor and acquiring point correspondences through analyzing the input images; a three-dimensional structure generator for generating a three-dimensional structure through three-dimensionally reconstructing the free parking space by using the feature points; a three-dimensional mosaic structure generator for generating a three-dimensional structure mosaic through reselecting the feature points to reconstruct the three-dimensional structure by using a de-rotation-based feature selection and mosaic the reconstructed three-dimensional structure by estimating a similarity transformation; a metric recoverer for acquiring metric information from the three-dimensional structure mosaic by using an image captor height ratio; and a free parking space detector for detecting the free parking space by estimating the positions of adjacent vehicles in the three-dimensional structure mosaic.