An essential oil diffuser comprises a main body and a power plug. The main body includes a shell, an electric circuit board, a connector shell, and an ultrasonic vibration module. Wherein, a receiving room is formed in the shell, an opening is formed at one end of the shell, and a shell hole is disposed on an upper shell. The connector shell is provided in the receiving room on a side of the shell opening. A receiving room is also formed in the connector shell, to receive an essence container screwed therein. The ultrasonic vibration module is disposed in the receiving room of the connector shell, and it is provided with an atomized liquid outlet corresponding to the shell hole and the connector hole, and is sleeved in the connector shell by means of a sleeve piece.
