The new generation of natural science teaching material in elementary school is the teaching material that utilizes inquiry-based learning in most parts of the tutorial and the provided material. The updating of teaching materials is an activity that must be carried out by the Universitas Terbuka to assure that the quality is following the development of science and knowledge. The study aims to test content, construct, and face validation along with the reliability by the experts upon the new generation self-directed natural science teaching materials in elementary schools following the scientific process. The validation process was conducted through Focus Group Discussion (FGD) in June 2019, which involved the interaction with the experts on teaching material, device, and media development. The instruments of teaching material validity are reviewed based on the content, construct, and face validity by employing Aiken's formula analysis for Content Validity Coefficient (CVC). Moreover, the instrument reliability is by using a One-way ANOVA analysis and Cronbach Alpha formula for Intraclass Correlation Coefficients (ICC). The results of validity assessment in average are CVC [greater than or equal to] 0.8 categorized as high validity and 0.4 < CVC < 0.8 classified as medium validity. The level of agreement reliability between experts generates the significance of p-value > 0.05. Hence there are no significant differences in the assessment of the experts. The level of the experts' reliability is on average of ICC [greater than or equal to] 0.8, which is categorized as good.