Since open inquiry of science was formally introduced at the 2007 Revised Science Curriculum Course, the purpose and effect of it has been positively evaluated, and it is underlined continuously until the revised science education course in 2015. However, through many previous studies, there is still a lack of awareness of open inquiry of both students and teachers in the field, and it was revealed they are continually appealing confusion and difficulties. Therefore, in this research, we analyzed the causes that make it difficult to execute open inquiry, and developed differentiated open inquiry guide materials that can contribute to the realization of teachers and students. They were developed by the brain-based evolutionary approach to provide students with authentic science. The brain-based evolutionary approach is reflecting the evolutionary attributes and the brain functions associated activities of scientists. It was revealed that, in the same way as the pilot test results, the usefulness of the differentiated guide materials were very high, and there was a statistically significant difference in the science attitude. It was found that the application of the brain-based evolutionary approach had positively influenced the stage of determining the inquiry themes, and self-confidence that could be able to do as a scientist. Analysis of top and sub group types on the basis of inquiry ability showed that both groups are improved at science attitude by the differentiated guide materials. There was a positive effect on change in the self-perception of scientific creativity. We were able to see a positive change in the post survey for open inquiry-efficacy. The developed differentiated open inquiry guide materials contributed to the improvement of open inquiry-efficacy for both the teacher and student.