Disclosed is a method of forming an electric wiring using inkjet printing. The method includes forming a main trench and first and second guide trenches on a substrate. The first and second guide trenches are disposed at opposite sides of the main trench. The method includes ejecting ink into the main trench, the ink including a conductive material. The method also includes heating the substrate to sinter the ink such that the electric wiring is formed an upper portion of the main trench, and contract the ink such that a tunnel is formed in a lower portion of the main trench.