The present study investigated how teachers' and students' beliefs about learning (cooperative or individual orientation) influence on help-seeking behavior including differences between elementary schools and middle schools. The participants were 575 elementary school students (4-6 graders) and 745 middle school students (7-9 graders). The results showed that elementary school students reported significantly higher levels of teachers' and own beliefs in cooperative learning than middle school students. On the other hand, middle school students reported significantly higher levels of own belief in individual learning and using help-seeking than elementary school students. Multiple population analysis revealed that teachers' beliefs in cooperative learning or individual learning, mediated by the same type of beliefs of students, influenced help-seeking behavior at either elementary schools or middle schools. These results suggest that it is important for teachers to change their beliefs about learning from individual-oriented to cooperative-oriented for promoting students' help-seeking.