<p>An optical modulator includes an acousto-optic medium (1) and a surface acoustic wave generating means (2) for generating a surface acoustic wave in the acousto-optic medium (1). A surface acoustic wave traveling region (3) where the surface acoustic wave generated by the surface acoustic wave generating means (2) is formed of the same material in the acousto-optic medium (1). The acousto-optic medium (1) has opposed first and second edge surfaces on both sides of the surface acoustic wave traveling region (3) in the direction perpendicular to the traveling direction of the surface acoustic wave. Both the first-order diffracted wave produced when the light entering through the first edge surface passes through the surface acoustic wave traveling region (3) and the light entering the acousto-optic medium (1) and propagating through the same while the operation of the surface acoustic wave generating means (2) is stopped exit from the second edge surface in different directions.</p>
