we propose a new double casting method using methanol to overcome the limitations of conventional methods. The hypothesis of this study is that the silane generated on the surface of the PDMS through plasma treatment can be combined with methanol to form a nanoscale coating layer. This coating layer sufficiently reduces adhesion between PDMS master mold and casting PDMS to ensure good separation during double casting. Methanol used as a coating material is mostly handled in general laboratories and is very inexpensive. In this paper, by using the double casting method, microstructures can be produced with high aspect ratio of 100 or more, various surfaces existing in nature can be duplicated, and complex 3D microstructures can be produced. The double casting method proposed in this study is very simple and can be applied directly to an unskilled researcher and it is possible to manufacture microstructure easily at low cost. Therefore, this technology can be integrated with micro technology in fields such as chemistry, biology, medicine, and material science, and it can be widely used for various applications. The development of this universal technique is expected to make a great contribution to the universal extension and industrialization of micro-technologies.