In this study, we explore a certain type of bullying - peer exclusion - focusing on the social network structure of a classroom and the role of social media in this process. Peer exclusion (“wang-tta” in Korean) is defined as a behavior that intentionally excludes victims from friendship circles and activities. In-depth interviews were conducted with 14 adolescents aged 14 to 16 years in South Korea. The findings demonstrate that peer exclusion there are two types of exclusion, namely, outsider type and inner relational type. In a class, there are usually several cliques or groups, and an outsider who does not belong to a particular group tends to be a target of exclusion. Inner relational exclusion usually occurs as a result of peer conflicts among members within the same group or clique. Distinct differences in the nature, reasons, and methods of exclusion between the two types of exclusion behavior were uncovered through the interviews. In particular, social media was employed in different ways depending on who the target is. The study raises the need for identifying the typologies of peer exclusion among adolescents and to better understand the underlying contexts of school bullying.