This research aimed to develop a definition maps-based plane geometry module to improve the student teachers' mathematical reasoning skills based on the level of Van Hiele. This development research was to produce a product in the form of a module at the college level. This research referred to the ADDIE model involving five stages, i.e. analyze, design, develop, implement, and evaluate. The instruments for data collection were observation sheet, Focus Group Discussion (FGD), assessment sheets, questionnaires, and test. The collected data then were analyzed using Aiken's validity, descriptive and inferential statistical analysis. The questionnaire instrument developed for student teachers was in a good category. The instrument used to test the effectiveness of the module was in a good category. A definition maps-based plane geometry module was in the criteria of feasible, practical and effective. The module was significantly developed in improving mathematical reasoning skills to rigor level.