Purpose -In Korea, cars are a mostly used transportation for the tourism purposes rather than public transportations, such as bus, train, and so on. However, the number of users for the high-speed rail in Korea have been rapidly increased since KTX opened in 2004. Thus, the purpose of this study is to examine the effect of opening high-speed rail on tourism demand and investigate the extent of high-speed rail’s opening effect on tourism demand by time line. Research Design, data, and methodology -The research design for this study is fold two parts. First, Reg-ARIMA was used to examine the causal relationship between the opening high-speed rail and the tourism demand in destination. Second, the size of effect due to the opening high-speed rail was identified by performing the counterfactual analysis, comparing the difference between the forcasted and real-measured number of tourists. The monthly time series data from January 2013 to December 2019 was used to conduct the empirical analysis. Result -The empirical results showed that the opening high-speed rail positively increased the tourism demand in destination with seasonal difference. Conclusions -The opening high-speed rail not only increases the tourism demand in the destination, but also disperses the demand for tourism during the off-season.