1. A stereo image matching apparatus, comprising: a window image extraction unit for extracting window images, each having a predetermined size around a selected pixel, for individual pixels of images that constitute stereo images captured by two or more cameras synchronized with one another; a local support-area determination unit for extracting a similarity mask indicating similarities equal to or greater than a threshold in a similarity image generated based on similarities calculated from differences between pixels of the window images, and for generating a local support-area mask indicating pixels of the similarity mask having neighbor connections to the center pixel of the similarity mask; a similarity extraction unit for calculating a local support-area similarity from a sum of the similarities of a local support-area determined by the local support-area mask; and a disparity selection unit for selecting a pair of window images for which the local support-area similarity is maximized, from among the window images, and then determining a disparity for the stereo images based on the selected window images.