In an electrodeposition system, the final quality of a coating is prevented from being degraded due to a coating material-containing aqueous solution flowing out of a steel plate mating portion during a drying process, while derivative problems such as an increase in the size of the system, an increase in the initial costs and the running costs, and a decrease in reliability are avoided. A washing zone that is subsequent to an electrodeposition zone in which an object to be coated is immersed in a coating material solution for electrodeposition so that a coating is formed on a surface of the object to be coated is provided with: a hot water washing tank in which the coated object is washed by being immersed in high-temperature washing water in the tank; and a spray washer that sprays a steel plate mating portion of the coated-object with high-temperature washing water, subsequent to washing in the hot water washing tank.