An apparatus and method are provided, which predict total nitrogen using general water quality data measured in real time. The total nitrogen prediction apparatus may include a regression model selection unit to select a regression model comprising general data of at least one water quality based on a correlation coefficient of the general data of at least one water quality, a quality-of-fit evaluation unit to evaluate quality of fit of the selected regression model, a regression model change unit to determine whether to change the regression model based on the quality of fit and change the regression model according to the determination result, and a total nitrogen prediction unit to predict total nitrogen of a body of water based on the regression model.