§47 APA of Taiwan stipulates the prohibition of the ex parte communications and follows the regulations in the APA of the USA. Since the APA in Taiwan came into effect in 2001, this regulation hasn’t stayed in the center of the legal researches and practice in Taiwan. However it plays an important role for the public officials in concrete cases. In order to clarify the meaning and the nature of this regulation, the similar regulations and the judicial decisions in the USA are first examined in this article. Meanwhile, the German legal system regarding this problem is also introduced. The judicial decisions in Taiwan will be also intensive observed. The application possibility of §47 APA of Taiwan as well as the viewpoints in the practice will be acquainted. At last, it becomes clear that the prohibition of the ex parte communications protects the fairness between the concerned parties in the formal hearing procedures, but not the neutrality of the responsible authority. The research shows that the nature of this legal institution has not been correctly understood in Taiwan. It leads to the result that the APA of Taiwan should be further reformed. An amendment of the APA of Taiwan is therefore recommended.