The aim of this study is to find out how designed Geometry Teaching Lesson affects candidate teachers' Van Hiele Geometric Thinking Levels. For that purpose, 14 weeks long study was performed with 44 candidate teachers who were university students in Turkey. Van Hiele Geometric Thinking Test was applied to candidate teachers before and after Geometry Teaching Lesson. Percentage, frequency and t-test were used for analyzing the data. When the data was investigated, it is seen that before Geometry Teaching Lesson, candidate teachers' geometric thinking levels and t- test points were really low, after lesson both their levels and t-test points made a considerable amount of progress. In this context, it can be said that designed geometry teaching lesson has an affect on upgrading candidate teachers' geometric thinking levels.