Learning devices must be in accordance with the appropriate learning model and the most possible to be applied in learning in accordance with the 2013 curriculum and the nature of physics so that learning becomes. This study aims to describe the validity and reliability of the cooperative learning model group investigation model to increase achievement motivation and thinking skills of students. The type of research used is research development (Research and Development) with the research model developed is the 4D Model which consists of define, design, develop, and disseminate. Retrieval of research data using validation sheets managed by 6 validator experts consisting of 3 physics education lecturers and 3 physics subject teachers. The research data is in the form of qualitative and quantitative data from the validator on the learning tools developed. These learning tools include syllabus, lesson plans, student worksheet, critical thinking skills tests, and achievement motivation. This study conducted a validity test to determine the feasibility and level of validity of the learning device. Data validity results obtained by an average value of 3.33 in the valid category. Furthermore, namely the reliability test, the average value of the reliability coefficient interval was 0.850 with the very high category. Based on these results, it can be seen that the cooperative learning model type of group investigation to increase achievement motivation and students' ability to think physics is valid and reliable used in learning activities.