This study uses meta-analysis to examine the effect size of twenty-two Cooperative Learning related research studies in Taiwan on student’s Learning Achievement, Affection Attitude, and Learning Outcome. The authors used computer program Meta-HC for analyzing data. The analyses revealed that Cooperative Learning had a positive affect on student’s Learning Achievement, Affection Attitude, Learning Outcome. However the effects size were low and moderate. Learning Achievement: d = 0.3256, Affection Attitude: d = 0.2573, Learning Outcome: d =  0.2870. In sum, Cooperative Learning has a positive effect on student’s Learning Achievement, Affection Attitude, and Learning Outcome. However, the effects are small. Thus, if a teacher wants to use Cooperative Learning as the main learning method in the classroom, he/she ought to consider the conditions and effects that might be caused by the methodological issues.