The purpose of this study is to investigate the roles of the aggression and the anger as mediators in relationship between the parent's overprotection and the cyber-bulling. In this study, the parent’s overprotection and the cyber-bulling are selected as independent and dependent variable respectively. And then the aggression and the anger are selected as mediators. For data collecting, 453 adolescents attending the second/third grade of middle school in Daegu are involved. The major findings are as follows: First, the parent’s overprotection is significantly associated with the aggression and the anger. Second, the parent’s overprotection is significantly associated with the cyber-bullying. Third, the aggression and the anger are significantly associated with the cyber-bullying. Finally, it is revealed that the aggression and the anger play a role as mediator in relationship between the parent's overprotection and the cyber-bulling. This study is important in that the fact the parent's overprotection is one factor of all causes of cyber-bullying is illuminated.