This study aims to improve the experimental method by making children think about causations of errors and mistakes in results focusing on the analysis of results of each group in the entire class. Results reveal that children become aware of different results corresponding to different groups under the same experiment and enrich the necessity of investigating their causations. Additionally, this study shows that making children recognize errors and mistakes in each experiment set by a teacher enables them to think about specific causations based on results of their own groups. As a result, this leads to improvement of the experimental method. In contrast, it is difficult for children to think about causations after the experiment when one child on behalf of the group carries out the experimental procedure.