For more than five decades, the outer space has been a stage of variety activities by states. In the cold war era, USSR and the USA located the outer space activities on the detailed competition agenda, showed having interest in the outer space, and were trying to take precedence of each other. This kind of activities gradually caught the attention of other great powers and as a result, the world has confronted with space proliferation especially in military dimensions in the last decades. In spite of new space law regime and existence of some limitations on military activities, little by little competition in the space particularly in military form became broader, more complex, and more critical than before, and has acquired remarkable place in international politics, too. Space based technologies have had dramatically effects on military and warfare planes, strategies, doctrines and tactics, which becomes a major factor in the 21st century for the assessment and measurement of states' national power. Militarization of the space and increasing the military space race among the great powers is the reality of this world that could not be ignored easily. With focusing on space politics, this paper will demonstrate the international competition in the space.