A method of preparing a silicon thin film, silicon thin film prepared using the method, and an electronic device including the silicon thin film are provided. The method includes applying an oxidized silicon element solution to a substrate and sintering the silicon oxide film to prepare a compact silicon oxide thin film, electrochemically reducing the silicon oxide thin film to form a porous silicon film, and re-sintering the porous silicon film. Therefore, the silicon thin film used in semiconductors, solar cells, secondary batteries and the like can be easily prepared at a low cost with a smaller number of processes than the conventional methods, and thus price competitiveness of products can be enhanced.