South Koreaʼs medical system is dualized into Western medicine and oriental medicine, and accordingly, the doctorʼs license and oriental medical doctorʼs license system are in operation. Until now, the Supreme Court has judged the criteria for determining whether an unlicensed medical practice is established for the use of diagnostic medical devices by oriental doctors as follows. First, the legislative purpose of the dual medical system, Second, the provisions and purposes of laws related to the medical practice, Third, the academic principles underlying the medical practice, and Fourth, the course, purpose, and appearance of the medical practice, Fifth, it is necessary to comprehensively consider whether medical schools and oriental medicine universities have secured expertise through curriculum or national tests, and to make a reasonable judgment in light of social norms. However, the recent Supreme Court's Decision 2016Do21314 Decided December 22, 2022 ruled that oriental doctorsʼs using an ultrasound diagnostic device did not constitute unlicensed medical practice. The criteria for judging the majority opinion of the en banc judgment are as follows. First, the relevant laws and regulations should prohibit oriental medical doctors from using the medical device. Second, in light of the characteristics of the device and the level of basic and professional knowledge and technology required for its use, oriental medicine doctors should use it as an auxiliary means of diagnosis. Third, in light of the circumstances, purpose, and appearance of the entire medical practice, it should be considered whether it is clear that the use of the diagnostic device by oriental doctors is irrelevant to the application and application of it based on the principle of oriental medical practice. Fourth, from the perspective of criminal justice, the meaning of oriental medical practice should be clearly and strictly interpreted from the perspective of oriental medicine doctors, it was judged that diagnostic medical devices should be excluded from criminal punishment unless it is clear that they are not related to the principle of oriental medical practice. The use of medical devices by oriental doctors presupposes or links to oriental doctorsʼ diagnosis and treatment behavior, and diagnosis has a significant role in determining whether to treat or not and setting treatment methods. This paper aims to reduce the possibility of harm associated with medical accidents and help establish a reasonable doctor and oriental medical doctor license system by comprehensively examining diagnostic medical devices that have been mainly problematic.