The 2013 curriculum provides a conception that the scientific approach to learning includes observing, asking, reasoning, creating, communicating. The scientific approach is appropriate for science because it is a student-centered learning approach and the learning process conforms to scientific criteria. This study aimed to investigate the effect size of the scientific approach on improving the science learning outcomes of Indonesian elementary school students. This study uses metaanalysis data in the form of descriptive exploratory quantitative. This study uses data collected in the form of journal articles, theses, and publication texts that are sought from the "Indonesia Onesearch" portal. Data analysis was performed by calculating the effect size of the same findings for similar problems. Results of tracing scientific publications obtained 20 documents published between 2013-2018 based on certain criteria. The results of this study indicated that the average effect size of the scientific approach to improving science learning outcomes of elementary school students is 1.1, including in the high category. The result of the effect size value shows that the scientific approach contributes 84%-88% to the improvement of science learning outcomes of Indonesian elementary school students. The implication of this research lies in the development of a scientific approach to various changes in the elementary school learning process following the mandate of the 2013 curriculum.