The aim of this study is to examine an existence of mutual interdependency in terms of military expenditure and arms imports between Northeast Asian countries such as South Korea, North Korea, China, Japan, and U.S. Recently, the mood of post cold war and intensified globalization lead to be disarmament in pursuing a policy on national defence in many countries. Since potential menace to national security has been receiving more concern rather than a direct armed clash, mutual interdependency on military spending should be fully understood. For a methodological tools, ${eta}$ and ${sigma}$-convergences, convergence with rational expectation, and Granger causality test are employed. Empirical evidence shows that the convergences which are evaluated by ${eta}$, ${sigma}$, and by a model based on rational expectation are in general revealed, and differences are more sensitive to a military decision making procedures. Granger causality, however, is not being existed. To this end, it would be concluded that the Northeast Asian countries are going with a trend in the world than forming their own tendency in this region.