During the last years, the number of fatalities from Heat Stroke during bathing is rapidly increasing. The body temperature during bath time changes depending on the water temperature and the bathing length. However, causal relationship between the way of taking a bath and fatality rate has not been evaluated quantitatively. In this study, authors have developed body temperature simulation model during bathing and have predicted the mortality and rate of hospital admission caused by Heat Stroke in order to prevent the bathing accident.