1. A video stabilization method, comprising the steps of: calculating optical flow vectors between original frames of a video; generating a regularization parameter to regularize undefined regions and the degree of motion smoothness of a desired stabilized video corresponding to the video according to the optical flow vectors; calculating smoothed optical flow vectors according to the regularization parameter and the optical flow vectors; and generating the stabilized video according to the original frames, the optical flow vectors, and the smoothed optical flow vectors.