The purpose of this study was to develop an instrument to measure the group efficacy in classroom, and teachers' work group. After reviewing of research on group efficacy in educational settings, A new version of the Group Efficacy Inventory was developed. In the Study1, A new version of the Group Efficacy in Classroom and School Moral Test was conducted by 233 elementary school students in the 5 and 6 grades. Factor analysis of scales of the Group Efficacy in classroom for elementary school resulted in 3 factors (Active commitment to life of classroom, Autonomy, Out-school activity). In the Study2, A new version of the Group Efficacy Classroom and School Moral Test was conducted by 303 secondary shool students. Factors analysis of scales of the Group Efficacy in Classroom for secondary school resulted in 2 factors (Activity of classroom, School celemony). In the Study3, A new version of the Group Efficacy in teachers' work group and organizational commitment test was conducted by 202 school teacheers. Factor analysis of scales of Group Efficacy in teachers' work group resulted in 3 factors (Organizational behavior in the school, educational goal, Pupils' guidance). Teachers who gave high weight to scales of the Group Efficacy in tearchers' work group had more positive evaluation of organizational commitment
