The purpose of this study was to examine the effects of adolescents’ game usage on game addiction and the mediation effects of withdrawal symptoms and loss of control. The subjects of the study was 6,499 elementary, middle and high school students included in the panel data from the survey conducted by The National Youth Policy Institute. For data analysis, SPSS WIN 21 and AMOS 21 programs were used to test the structural equation model by examining the relationships among game usage, withdrawal symptoms, loss of control, and game addiction. The results are as followings. First, adolescents’ average daily game playing hours and average daily game playing hours on holidays caused withdrawal symptoms and loss of control, increasing the possibility of game addiction. However, the relationship between the number of years of playing games and game addiction was not mediated by withdrawal symptoms and loss of control. This implies that playing computer games from young age does not necessarily lead to game addiction unless the students show withdrawal symptoms or lose control.