A method for plating a belt substrate including conveying a belt substrate through a plating tank, contacting an immersed cathode power-supply device and/or an auxiliary cathode power-supply device with the belt substrate conveyed into the interior of the plating tank such that the belt substrate becomes a cathode, and electrically plating a surface of the belt substrate in the interior of the plating tank while the immersed cathode power-supply device and/or the auxiliary cathode power-supply device maintains cathode power-supply to the belt substrate conveyed into the interior portion of the plating tank. The immersed cathode power-supply device and the auxiliary cathode power-supply device are positioned in the interior portion of the plating tank and are electrically connected by a short circuit wiring.