The purpose of this thesis is to research on the process how the interaction between the United States and South Korea during the Cold War period had formed Korean nationalism and how that Korean nationalism has been transformed in the post Cold War period with the recent anti-American sentiment in Korea. The end of the Cold war makes the characteristics of Korean nationalism different. Before the end of the Cold war Korean nationalism can be characterized as "state-centered" nationalism. Park, Chung-hee regime especially put so much emphasis on the "developmental state" strategy that people and all the resources were highly mobilized and exploited by the government. Moreover, under the atmosphere of the Cold war period South Korea had nothing but to keep good relationship with other states to get aids from those countries, especially the US, against the possible threat of North Korea. In the post-Cold war era, however, South Korea and the US have changed their attitudes toward each other and even nationalist demonstration, such as anti-American sentiment, has occurred in South Korea. For instance, in 2002 when two Korean middle school girls were killed in a traffic accident by American GIs, it accelerated anti-American sentiment and strong nationalism in South Korea. The "external collective identities" of two actors are formulated in the process of the interaction and so do South Korean people and the USFK. In their interaction by giving and taking identities they also form and sometimes change their "internal collective identities". In this learning process, Korean people formulate and sometimes change their "external collective identity" toward the "other" - the US, as well as the "internal collective identity" of themselves.