Extreme temperature has direct and indirect effects on Human Health, and usually influences negatively. This study analyzes the correlation between extreme temperature and excess mortality caused by cardiovascular disease in Seoul. Excess mortality correlates with daily maximum temperature, especially daily excess fatality over two standard deviations, has a strong positive correlation. On the other hand, daily minimum temperature is not significantly related with excess death. Recently, significance of the correlation coefficient of high temperature in August decreases because of the heat wave preparation.