The purpose of this study is to validate the effect that the parent attachment, peer relationship and internet immersion would have on ego identity of adolescents. The subjects of this study are a total of 857 adolescents consisting of 206 middle school students, 559 adolescents of liberal arts high schools, and 92 adolescents of vocational high schools. The parent attachment scale used in this study is the revised version(IPPA-R) of the Inventory of Parent and Peer Attachment(IPPA) of Armsden and Greenberg(1987) which was translated by Ok Jeong(1998), while the peer relationship used in this study is the peer relationship scale reconstructed by Kim Jae-Eun(2007). For the ego identity scale, we used the ego identity test sheet reconstructed by Song Hyeon-Wook(2008). Moreover, the internet immersion measurement tool used in this study is the Korean Internet Addiction Proneness Scale(K-scale) developed by Kim Cheong-Taek, Kim Dong-Il, Park Jung-Gyu, and Lee Soo-Jin(2002). The collected data were processed for correlation analysis and multiple regression analysis. The results of this study are as follows: The parent attachment of adolescents had a significant influences on their ego identity while the peer relationship of adolescents also had a significant influence their ego identity. However, internet immersion had a negative influence on ego identity. In other words, ego identity increases higher when the extent of parent attachment is stronger and peer relationship is more positive. By contrast, ego identity decreases lower when the extent of internet immersion is higher.