The utility model discloses a ultrasonic milling device, which relates to the technical field of ultrasonic milling, and comprises a knife body, a ultrasonic energy converter and a knife, wherein the ultrasonic energy converter is of a cylindrical structure which is connected with a derived cable, the diameter of an upper half segment of the ultrasonic energy converter is bigger than the diameter of a lower half segment, the middle of the ultrasonic energy converter transits by adopting a truncated cone, a first flange plate is integrally formed on the upper end of the truncated cone, a thread hole which is adaptive to the first flange plate is arranged on the lower end surface of the knife body, the knife is concentrically and fixedly assembled on the lower end of the ultrasonic energy converter, an installation cavity which is adaptive to the ultrasonic energy converter is arranged on the lower end of the knife body, the inner wall of the installation cavity is contacted with the outer wall of the ultrasonic energy converter, a bearing device and a power supply device are orderly assembled on the outer wall of the lower end of the knife body from top to bottom, a cable derived hole which is arranged on the position of the power supply device is arranged on the knife body, and the ultrasonic energy converter and the knife body are concentrically and fixedly assembled together. The ultrasonic milling device can greatly improve industrial applicability of ultrasonic milling technology when milling hard materials.