Mathematics is a science that deals with ideas or concepts in the abstractreasoning. Mathematics has a different understanding of the concepts of science another. Inmathematical understanding many factors that are indicators of the achievement of themathematics understanding. The understanding gained from the process of learningmathematics. One of the factors that affect the learning process is the student of mathematics.Students will understand the math properly understanding their math based on themathematical concept it self. To analyze student understanding of the concepts ofmathematics, teachers must determine the level of mental development of the students. Anunderstanding of the mathematical concept is the result of construction and reconstruction ofmathematical objects. Construction and reconstruction is done through activities such asmath actions, process, objects are organized in a scheme to solve the problem. One theory oflearning that can be used as a reference to see the students' understanding of mathematics isthe theory APOS (Action, process, Object, and Schema). APOS In theory, there may bestudents who did not start through the early stages of APOS theory is action, there may bestudents who started from the object passed next stage. So do not rule out the possibilitythat, if the students are already in the stage of an object or even a scheme, then the studentmay not need to go through the stage of the process. This is because the proces oftransformation has been interiorized perfectly into the minds of students. APOS theory canbe used to analyze the cognitive structure of the student in understanding