Critical thinking skills are very important in everyday life, because critical thinking skills can develop thinking skills, such as the ability to make decisions and solve problems. The purpose of this research is to describe the students' critical thinking process in solving math problems. Critical thinking process in this study refers to the four stages of gathering information, evaluates of information, making solution, and evaluates the Conclusions. In each stage covers various aspects that is at the stage of gathering information includes identifying all of the information, connect the relevant information, grouping information in accordance with sections each each, and set goals that are asked in the problem based on the information. Stages of evaluates of information include Selecting all information is important, establishing the assumptions of the information in the problem, linking important matters of information based on assumptions and identifying possible strategies to solve the problem. The making solution stage involves predicting the completion steps that are from the information, and processing the completion steps, and establishing the completion result. Stages evaluates the conclusions include Establishing confidence of problem solving outcome, and clarifying problem solving results. This research is a qualitative case study strategy and research place in SMP Negeri 1 Gresik. The material used is a daily problem. To analyze the process of students' critical thinking in solving. The results show that the student performs the complete critical thinking process in solving the problem. But experiencing the error of selecting information caused in the processing of information S1 experiencing misunderstanding and recall the semantic memory. And S1 conducts critical thinking process through four stages: gathering information, evaluates of information, making solution, and evaluates the conclusions is complete but experiencing divided attention in setting assumption.