An acousto optic element comprises optically transparent acousto optic medium having light incoming plane, light outgoing plane facing light incoming plane, transducer joining plane, and inclined plane tilted to transducer joining plane and piezoelectric transducer on which two opposing planes i.e., electrode layers and are formed and the transducer is connected to transducer joining plane of acousto optic medium through one of the electrode layers, wherein a deposited layer or a coating layer is formed on at least one of ultrasonic transducer or the acousto optic medium, the layer preventing ultrasonic waves generated by oscillation of ultrasonic transducer leaking onto acousto optic medium as a leakage-ultrasonic wave and propagating there, thus obtaining a high light-fading ratio.