Provided is a spin coating apparatus having a ring-shaped or polygonal auxiliary member for use in manufacture of a coated substrate via spin coating, wherein the auxiliary member is positioned adjacent to the side of a substrate for coating, within a range of a spaced distance of 0.03 to 0.8 mm and a range of a height deviation of less than 0.1 mm, upon mounting the substrate. When a surface of a substrate for coating is spin coated with a coating agent using the apparatus of the present invention, it is possible to eliminate or effectively reduce a ski-jump phenomenon at end portions of a coated substrate occurring when spin coating is performed, thereby resulting in uniform coating of a coating solution on the substrate, and it is also possible to effectively decrease contamination of the substrate for coating due to inflow or stay of the remaining coating agent.