Abstract: An atomization mechanism of an aroma diffuser includes an atomization shell and an essential oil bottle. The essential oil bottle is provided with a first cavity, and the atomization shell is provided with a second cavity. When the atomization mechanism is placed normally, pressure exerted by a ball on a spring can compress the spring, making a second communication hole of a leakage-proof cover open. When the atomization mechanism is tilted, pressure exerted by the ball on the spring is not sufficient to compress the spring, and the spring stretches to make the ball abut against at least a portion of the leakage-proof cover, so that the second communication hole of the leakage-proof cover is closed.