The purpose of this study is to clarify the motivation of adolescent volunteers based on exchange theory by analyzing benefits and costs. The activation for family-volunteering is explored to decrease the cost of volunteering. Data were collected from 463 adolescents and analyzed using SPSS 16.0 program. The statistics used for analysis were the factor analysis, cluster analysis, T-Test and ANOVA, Findings indicated that a 75.2% of adolescents participated in voluntary activities during last one year, but a 90.3% of subjects was not taken part in family volunteering. Family volunteering has not been activated but adolescents hoped high to participate with family. Adolescents evaluated high the cost of family time lost because of volunteering. The clusters evaluating the costs of volunteering low participated more than other clusters. From these results, it was proposed that costs of volunteering such as conflicts with members of family or supervisors should be lessened than the benefits of it emphasized. The family volunteering is suggested to decrease the cost of family time loss.