This study aims to forecast the size of the market considered for seasonality based on past demand data and present a demand prediction model for whale ocean travel ships of whale tourism in Ulsan, Korea. For this, this study collected data from January 2010 to December 2020 from Tourism Knowledge & Information System. In order to achieve the research purpose, a time series analysis of Seasonal ARIMA which is widely used in econometrics was conducted. We intend to compare predictions and observations obtained using the Seasonal ARIMA, that is, the autoregressive moving average model, test the suitability and accuracy of the model, and select the most suitable model which is Seasonal ARIMA(1,1,2)(0,1,0). The result was forecasted that the number of tourism destinations was 10,624 in first quarter 2021, 19,530 in second quarter 2021, 46,577 in third quarter 2021, 45,886 in fourth quarter 2021, 15,836 in first quarter in 2022, 32,817 in second quarter 2022, 40,012 in third quarter 2022, 41,090 in fourth quarter 2022, 19,129 in first quarter 2023, 35,717 in second quarter 2023, 34,960 in third quarter 2023, 37,580 in fourth quarter 2023.