The invention discloses an ultrasonic milling device and a control process, relating to the technical field of ultrasonic milling. The ultrasonic milling device comprises a cutter body, an ultrasonic transducer and a cutter, wherein the ultrasonic transducer is of a cylindrical structure which is connected with an export cable; the diameter of the upper half section of the ultrasonic transducer is more than that of the lower half section, and the middle part of the ultrasonic transducer is in transition in a truncated cone form; a first flange plate is integrally formed to the upper end of the truncated cone; a threaded hole adaptive to the first flange plate is formed in the lower end surface of the cutter body; the cutter is concentrically fixedly assembled at the lower end of the ultrasonic transducer; a mounting cavity adaptive to the ultrasonic transducer is formed in the lower end of the cutter body; the inner wall of the mounting cavity is in contact with the outer wall of the ultrasonic transducer; a bearing device and a power supply device are assembled on the outer wall of the lower end of the cutter body from top to bottom in sequence; a cable outlet hole is formed in the part, equipped with the power supply device, on the cutter body; the ultrasonic transducer is integrally fixedly assembled to the cutter body in a concentric manner. With the adoption of the ultrasonic milling device for milling a hard material, the industrial practicability of the ultrasonic milling technology can be greatly improved.