<p>The present invention relates to an ultrasonic diffuser which can be used while floating in a cup or container filled with water. Provided is the ultrasonic diffuser which includes: a lower body which applies ultrasonic vibrations to the water flowing into the bottom surface thereof so as to be disintegrated into water particles; an ultrasonic oscillation element which is coupled to the inner portion of the lower body in order to apply ultrasonic waves to the water which is to be disintegrated into fine water particles; and an upper body which is coupled to the upper side of the lower body and disintegrates the water while floating on the water so as to discharge the fine water particles. The present invention has a simple structure and simple components for greater portability, can be conveniently used as a diffuser for individual use in a narrow space, and alleviates the inconvenience of cleaning a water tank and the concern of bacterial reproduction since the diffuser of the present invention is used while floating in a cup or container filled with the water.</p>
