In this paper, we propose a new watermarking technique for copyright protection of stereo image. The proposed technique embeds watermark to the region which corresponds to occlusion of the disparity map to be extracted by the proposed stereo matching and the frequency coefficient with the appropriate value. We use discrete wavelet transform for frequency transform tool. The proposed algorithm consists of stereo matching, watermark rearrange, mark space selection, and watermark embedding/extracting. We tested the experiment about 4 stereo images which are from Middlebury site. We embedded the watermark to 4 stereo images and extracted it from the images after attacks. We also visually analyzed the watermark embedding images in 3D TV environment.