The invention belongs to the field of film coating, and in particular relates to a method and a device used for coating a single side of a rigid substrate. In a coating device provided by the invention, a rectangular groove in the centre of an installation groove is provided with an inner rubber pad and the rigid substrate in turn; an outer rubber pad and a gasket are arranged outside of the rigid substrate in turn; a rectangular hole structure is arranged between the outer rubber pad and the gasket so that a coating surface of the rigid substrate is contacted with coating liquid; the installation groove, a fastening groove and the rigid substrate are connected with each other through screws and are placed into a coating groove filled with the coating liquid; and the installation groove and the fastening groove are respectively connected with a polar plate, a direct current power supply, a voltmeter and an ammeter electrically in turn. The coating method provided by the invention comprises the following steps of: pre-treating the rigid substrate; placing the pre-treated rigid substrate into the coating device; placing the coating device into the solution of a coating material; and exerting an electric field to form a single-layer or multilayer coating. Due to the adoption of the method and the device, the coating is performed on the single side of the rigid substrate; and the thickness of a coating layer can be controlled at nanoscale.