The main purpose of this study is to clarify a guiding principle for guaranteeing chances of evoking and resolving cognitive conflict on mathematics classes. The hypothesis of this study is when a chance of evoking and resolving cognitive conflict is guaranteed, children will reorganize the concept they have already had and make them change to a more objective. scientific one. This paper analyzes the effectiveness of the learning process model for guaranteeing chances of evoking and resolving cognitive conflict through experiment classes. Subjects of survey were sixth graders of an elementary school. A teaching of a unit study of 3 hours was performed. The problems chosen as learning materials for investigation were the ones of "understanding of the concept of the ratio" from the National Assessment of Academic Ability. As a result of pre-post assessment of performance and investigation problems, the effectiveness of the learning process model was significant. and it was improved by the individual analysis of subject children.