The invention provides a method of manufacturing a brush plate. Brush plates used in a brush motor are manufactured according to the following steps: first, combining an upper mold that molds the upper surface of the brush plate, a lower mold that molds the lower surface of the brush plate, and a slider mold that molds the inner surface of a brush holder; next, molten resin flowing into a cavity formed by the upper mold, the lower mold, and the slider mold; next, curing the molten resin in the cavity; and finally, opening the upper mold, the lower mold and the slider mold, and taking out the molded brush plate. The upper mold has a flange upper surface molding portion that shapes the upper surface of a flange portion. Further, the slider mold is disposed above the flange upper surface molding portion. Therefore, the slider mold is independent of the molding of the upper surface of the flange portion. Therefore, no parting line due to the slider mold is formed on the upper surface of the flange portion.