The 1967 Outer Space Treaty(OST) celebrates its 50th anniversary in 2017. This article deals with the OST"s retrospect during the fifty years of the Treaty and its prospect in international law. Main subjects of this article focus on the followings: Freedom of Exploration and Scientific Research in Outer Space, Prohibition of National Appropriation, Application of International Law, Peaceful Use of Outer Space, Rescue and Return of Objects in Outer Space and Astronauts, International Responsibility for States’ Activities in Outer Space, Registration of Space Objects and Exclusive Jurisdiction, Respect for the Rights of Other States, Duty of Openness and Transparency in the OST. Because of the rapid development of space science and technology there is a need that there must be a new treaty instead of the OST for solving the current problems raised in the exploration and use of outer space. However, in retrospect of the fifty years of the OST some principles such as the freedom for exploration and scientific research in outer space, the principle of non-appropriation, and the principle of the respect of other countries’ rights in the OST have become customary law and jus cogens in international law. Furthermore the principles of global public interest in outer space in the OST imposes international obligations erga omnes applicable to all States. As customary international law, the OST reflects some rules that bind even those states who are not formal parties to the treaty itself. The present framework of space law incorporates a substantial body of rules in the form of treaties and sets of principles. In order to supplement the shortcomings of the space treaties there have been many soft laws such as recommendations, declarations and resolutions adopted by international organizations and regional communities. The OST represents the most fundamental and all-encompassing of the space treaties, and hence the foundation for all of space law. Thus the OST should be not only an international agreement of high importance as the constitution of outer space establishing rule of law in outer space, but also a manifesto of genuine expectations of all segments of mankind. It is therefore imperative that not only the letter but also the sprit of the OST govern space activities of States. Activities contrary to both the spirit and letter of the OST would shatter the belief in the rule of law and in the international democratic law-making process.