The purpose of this study was to examine the relationship between the smartphone use and exercise behavior among senior high school students in Tainan City. In particular, levels of smartphone addiction were entered in the regression model to predict students' exercise behavior. A convenient sampling method was used to collect data through distributing 450 questionnaires in different senior high schools located in Tainan City. A total of 382 valid subjects were obtained. Using SPSS for Windows 17.0, the collected data were analyzed with statistical procedure of descriptive analysis, Independent t-test, Independent One-Way ANOVA, and stepwise multiple regression analysis. Variable of smartphone use time could significantly predict students' exercise behavior. Specifically, variables of ”daily activity” and ”time allocation” could explain up to 35.1% variance of students' exercise behavior. It is suggested that students should have a routine schedule for their daily life so that they might avoid the negative influence of smartphone use on their exercise behavior.