This study aims to describe the critical thinking skill of high performance mathematics teacher in solving mathematical problems with the subject was a junior high school teacher who was awarded as a high performance teacher. Qualitative research method was used to reveal the critical thinking skill of a high performance mathematics teacher, data collection gathered through in-depth interviews based on mathematical problem solving tasks. The results indicate that critical thinking skill of high performance mathematics teacher in solving mathematics problem. In Focus, teacher mentioned the information asked in the problem and developed it to formulate problem solving planning. In Reason, teacher stated the idea of problem solving with relevant reason. In Inference, she checked how confident the reason is given to support the problem solving argument. In Situation, teacher understood important information and situations in the problem given. In Clarity, teacher explained the terms used in the argument correctly and provided another example of a case similar to the given problem. In Overview, she checked the compatibility between problem information, completion strategies, and final solutions. The high performance teacher have abilities of ideal critical thinker. From the results of study, it is expected a learning that facilitates critical thinking can be developed.