The purpose of this study was to clarify the effects of participation in “Hiroshima Kids City 2012" as a volunteer on change of students' self efficacy regarding teaching profession and of their cognition of abilities needed for teachers. Participants were 12 students who took part in “Hiroshima Kids City 2012". The results showed that their self efficacy regarding following categories were improved; children's group formation, planning and progressing the activities, and cooperation with business people. We also found that many students' cognition of abilities needed for following categories changed; development of children's autonomy, and cooperation with business people.