The present invention relates to an acousto-optic device capable of improving the interaction efficiency for suppressing the driving power needed for SAW generation. The acousto-optic device according to the present invention a substrate showing an acousto-optic effect, first and second optical waveguides formed on the substrate to be substantially parallel with each other for propagating light, a transducer formed on the substrate for producing a surface acoustic wave to be propagated in a propagation direction along directions of the first and second optical waveguides, and a surface acoustic wave distribution structure for distributing an intensity of the surface acoustic wave from the transducer in a direction perpendicular to the propagation direction on the substrate so that maximum values develop at two points corresponding to positions of the first and second optical waveguides.