The purpose of study was to measure the tourism seasonality, comparing different regions in Korea. In the empirical analysis, this study measured and analyzed the seasonality of Gangwon and Jeju province tourism for the recent 13 years(1998-2010) and analyzed Gini`s Coefficient, Seasonality ratio, the regression between the root causes of the seasonality and the tourism demand. The empirical analysis result showed that the demand was concentrated in October for Gangwon province tourism and meant that those months had higher seasonality than other months. Especially, Gangwon province tourism showed higher seasonality and shows imbalance of the number of tourists. On the othe hand, Jeju province tourism relatively showed balance of the number of tourists. Therefore Gangwon province is relatively more affected seasonality than Jeju province. This study would be a great help to understand the imbalanced tourism demand and could be used to supply the necessity and set the strategy to decrease tourism seasonality for the province tourism.