Ultrasonic beauty knife

The invention particularly relates to an ultrasonic beauty knife which comprises a shell, an ultrasonic output unit, a focus point adjusting mechanism, a detection mechanism, a control unit and a power source, and the focus point adjusting mechanism is used for adjusting the action depth of an ultrasonic focus point emitted by the ultrasonic output unit on human skin. The detection mechanism is used for detecting the moving distance of the ultrasonic output unit on the human skin acting face and feeding back the moving distance to the control unit, and the control unit controls the ultrasonic output unit to conduct ultrasonic dotting on the human skin acting face according to the preset moving interval. The ultrasonic beauty knife is simple in structure, convenient to use and high in safety, and a user can flexibly adjust the ultrasonic beauty knife to a proper action depth of an ultrasonic focus point according to different treatment positions, so that a better treatment effect is achieved; and the ultrasoni