This thesis analyzed the reasons of foreign currency crisis which happened in Mid-South America and South East Asia based on the economical structure of developing countries. First, it is illustrated theoretically. Since the developing countries, which maintain the export-oriented economic growth, allocates the sources in the trade area, equilibrium real exchange rate of these countries get relatively higher evaluation. Capital inflows with future exports as its necessary conditions make the foreign exchange market participants expect that the real future exchange rate will be much lower than the current equilibrium exchange rate (so called “devaluation”), giving rise to foreign exchange crisis. Negative debts result in the information asymmetry between creditor and debtor, and between adverse selection and moral relaxation, and that cause crisis for foreign currency and reduces their attractiveness, proposed by Mishkin. In fact developing countries in Southeast Asia and Central and South America that has the recent outbreak of a foreign exchange crisis, also have unhealthy banks. When we apply analysis mentioned above to South Korea, we can not find evidence of relatively high evaluation level on the real equilibrium exchange rate and evidence of poor management in the banking sector.