The purpose of this study was to analyze the effects of collaborative activities on group identity in a virtual world such as "Second Life." To achieve this purpose, this study adopted events that promoted participants' interactions using tools inherent in "Second Life." The interactive tools given to the control group in this study included "permissions to move, copy, edit", "give item", "chat", and "send instant message". In addition to these tools, special tools of "give item for praise" and "pollster" were given to the experimental group. The two groups were compared using scores of group identity, which has nine subcategories. The experimental group showed higher scores in five subcategories than the control group. Thus, we concluded that the use of tools for facilitating participants' interactions is effective for the formation of group identity.