In this paper, we propose a foreground extraction method in stereo images. We exploit disparity, which is inversely proportional to depth value. Using plane-induced homography, we model the disparity of background region beforehand. Then the probability of a pixel being foreground is calculated by measuring plane-induced parallax, the difference between the estimated position of corresponding points by plane-induced homography and the actual position of the corresponding points, Experimental results show that our method can be used as an alternative method for stereo image foreground extraction.