Development of social exclusion judgments regarding out-groups, also known as “the left out”, was investigated.  In Study 1, judgments about the social exclusion of others having behavioral characteristics corresponding to 3 domains (moral, conventional, personal) in social domain theory were tapped by the question, “Do you agree to exclude people from your group?” Reasons for that judgment and conformity judgment were tapped by the question, “Should excluded children change themselves to fit into a group?” Elementary school (57 fourth graders, 67 sixth graders), junior high school (67 eighth graders), and university students (n=64) responded to these questions with respect to personal groups (playmates) and public groups (teams).  The results of Study 1 indicated changes in judgments with increasing age, changing from focusing on the unfairness of exclusion without distinguishing the characteristics of those who are excluded, to judgments that distinguished the excluded others’ characteristics in detail and focused on group functions and objectives.  The elementary school students made judgments that distinguished the 2 groups ; they tended to indicate that the excluded children should change.  In Study 2, the relation between social exclusion and differences in orientation toward groups and friends was examined; participants were elementary school (65 fourth graders, 62 sixth graders) and junior high school (54 eighth graders) students.  The results suggested that when orientation to a closed and fixed group, and demand for conformity with friends, were high, exclusion from a group tended to be accepted.