The aim of this study is to describe an explanatory approach for analyzing logical structures of science teachers’ inference process with epistemic tools. The epistemic tools used in this study were the following concepts of epistemology: Inference to the Best Explanation (IBE), Explaining to the Best Inference (EBI), testimony, and theories of scientific explanations. The online problem-solving activities in science teachers’ Community of Practice (CoP) were analyzed. The result shows their professional competence to do scientific investigation in CoP. The logical structure of science teachers' problem-solving activities also suggests some ideas to design students' exploring activities in class.