In Japan, a Medical Doctor (M.D.) is referred to as a “Medical practitioner” in medical law. The Medical Practitioners Act was enacted three years after the promulgation of the Constitution of Japan. According to Article 1, “Medical practitioners shall contribute to the improvement and promotion of public health by providing medical care and health guidance, thereby ensuring the healthy lives of the people.”. As can be seen from using the phrase “improvement and promotion of public health” in Article 25 of the Constitution (see Chap. 2), medical practitioners are expected to approach their duties with a mindset that respects human life and dignity. They are expected to treat illnesses and injuries and take the lead in improving and promoting public health in all fields. Medical practitioners must be professionals in both clinical medicine and public health.