A plating method for pre-plating or plating a cylinder inner peripheral surface to be treated of a cylinder block by introducing treatment liquid to the cylinder inner peripheral surface by using a plating apparatus provided with a sealing jig having a sealing member and an electrode to which the seal jig is mounted includes the steps, which are performed successively: sealing the cylinder inner peripheral surface by bringing the sealing jig into contact with the cylinder inner peripheral surface; introducing the treatment liquid to the cylinder inner peripheral surface; and treating the cylinder inner peripheral surface by applying predetermined charge to the electrode of the plating apparatus and the cylinder block to thereby perform pre-plating or plating process in a state that a liquid to be treated fills a space including the cylinder inner peripheral surface. In the method, the treatment liquid introducing step is performed after confirmation of sealing by the sealing step.