This study is to investigate the effect of cooperative learning in an integrated class on students with and without disabilities in an elementary school. The study targeted one class selected the lower grades. Cooperative learning was conducted twice per week for the nine weeks regular class with for two students with special needs who were being educated in part-time and 11 normal students from the school. In order to find out the possible change after cooperative learning in the target action and class participation of the special needs students, the incidence of a target action were recorded as a reverse design and shown with a table and a graph. In addition, to look at the change which affects the normal students’ prosocial action and their adaptability to school, the measurement results of the experiment of before and after cooperative learning went through descriptive statistics and counterpart t-verification. The results are as follows. First, before cooperative learning intervention, students with special needs neither got involved in the class nor were they cooperative. Often they showed target behaviors. However, after the cooperative learning intervention, they are participated in the class fairly well, interacting with their friends and doing on-task behaviors. Second, the results of their prosocial action and their adaptability to school before and after the experiment were examined after the cooperative learning was applied to students without disabilities. The results showed significant differences in the factors such as giving help to, protecting, sharing with and cooperating with the students without special needs in terms of prosocial action, and also in the factors such as the teacher -student relationship, classes in school, and school rules in terms of the adaptability to school. Based on the results and discussion of this study, it is concluded that cooperative learning in the integrated class turned out to have a positive influence not only on the special needs students’ target action and their class participation, but also on the normal students’ prosocial action and their adaptability to school. Here, several suggestions were discussed for a follow-up study. First, a study on how much of an intervention period is needed. Second, various class situation can be employed and tested for generalization. Third, a follow-up study on another teaching-learning acitivity different from cooperative learning is needed.