Mathematical communication ability of students allows them to be able to communicate ideas or mathematical ideas with symbols, table, diagrams, or other media to clarify the situation or problems and discuss them with others. But, based on the observation students have difficulty in communicating their ideas. Mathematical communication ability of students needs to be improved. It is suspected to do with the learning of mathematics based of APOS mental constructions. This study tries to developed mathematics worksheet based of APOS mental construction. The students had been given instructions that guide them to understand the studied material. The next process, student had to repeat activities that had been performed previously using different examples. Then the student concluded from the two activities that had been done. The final scheme, students find the relationship of the material that had been studied. The purpose of this study is to develop Student's Work Sheet based of APOS for seven Grade Students of Junior High School that are valid, practical, and effective. This research is the development research using Plomp's Model which consists of three phases, preliminary research, development or prototyping phase, and assessment phase. This research finds that the Worksheet is valid and practices.