Summary Professor Taro Sakai’s (Professor of the Graduate School of Law, Hitotsubashi University; and researcher at the Institute for Global Governance Research) article was published in the July 2022 version of the Hitotsubashi Journal of Law and International Studies. The Japanese Companies Act does not allow corporations to become a board member (Section 331 subsection 1 item 1). This paper examines whether this rule can be theoretically justified. Moreover, this paper also analyses whether there is policy legitimacy or technical significance in a corporation becoming a director. This issue has long been discussed, but with the enactment of the Companies Act in 2005, the major structure of the regulation on which the discussion is based has changed significantly. This paper discusses the eligibility of a corporation to become a board member in terms of whether this change in the corporate regulations affects the rationale as illustrated in the previous discussions.