The Collaborative Based Science Learning (CBSL) model is a collaborative science-based learning that is used in science learning to improve the critical thinking skill and responsibility of junior high school students. The syntax of CBSL model includes: 1) Motivation and problem orientation, 2) Collaborative-based critical thinking activity, 3) communicating the results of collaborative critical thinking activity, 4) Advance practice of critical thinking and responsibility, and 5) Reflection. The purpose of this study is to analyze the validity and reliability of CBSL model that has been developed to improve the critical thinking skill and responsibility of junior high school students. The validity and reliability data of CBSL model is obtained through Focus Group Discussion (FGD) activities. The single measures inter rater coefficient correlation (ICC) and Cronbach's coefficient alpha was used to analyze the validity and reliability of the CBSL model. The results showed that CBSL Model has fulfilled the validity requirements (rα = .86) and reliability (α = .98), so the CBSL Model qualified the validity and reliability. The implication of this research is that the valid and reliable CBSL models can be used to improve students' critical thinking skill and student responsibility theoretically. Further research can be conducted to test the practicality and effectiveness of the CBSL Model to improve the critical thinking skill and responsibility of junior high school students.