The purposes of this study were to examine the educational effects of cooperative learning activities as a teaching method in kindergarten. The questions of this study were followings : 1. Are there any effects of cooperative learning activities of children`s cognitive competences? 2. Are there any effects of cooperative learning activities on children`s social competences? 3. Are there any effects of cooperative learning activities on children`s social play? 4. Are there any effects of cooperative learning activities on children`s competences of educational activities? The subjects were 43 children for the experimetal group and 36 children for the control group in kindergarten. The experimental group was conducted by the coorperative learning activities for one semester. To examine educational effects, the data were collected by the time sampling observation of social play and the tests of intelligence, social competences, and competences of educational activities. The results of study were as follows : 1. There were significant differences between the experimental group and the control group on children`s cognitive competences. The cooperative learning activities showed the positive educational effects on children`s intelligence. 2. There were significant differences between the experimental group and the control group on children`s social competences. The cooperative learning activities showed the positive educational effects of children`s social competences. 3. There were significant differences between the experimental group and the control group on children`s social play. The cooperative learning activities showed the positive developmental changes in children`s social play. 4. There were significant differences between the experimental group and the control group on competences of educational activities. The cooperative learning activities showed the positive educational effects of children`s competences of educational activities. This study suggested that early childhood educators should develop the program based on cooperative learning activities to increase children`s competences in kindergarten.