A method of manufacturing a toothed part having both structures of a drive plate and a ring gear, comprising: a first process of forming, by performing a folding processing to an end portion of a material, a portion to be processed having a structure, in which a plurality of layers respectively having a thickness corresponding to a plate thickness of the material overlap each other, in the material such that a plate thickness direction of the layer is orthogonal to a plate thickness direction of the material; and a tooth forming process of changing, by performing a forging processing to the portion to be processed, a shape of the portion to be processed to a target shape while press-welding the layers of the portion to be processed to each other by plastic deformation, the method being characterized in that the first process includes: forming a first formed part having a cup bottom portion and an annular standing wall portion by folding an outer circumferential portion of the material by 90° into an L shape by drawing; forming a second formed part having a two-plate stacked outer circumferential portion by folding the standing wall portion by 90° so as to be overlapped on the cup bottom portion; and forming a third formed part (11C, 11D, 11E) having a two-plate stacked standing wall portion as the portion to be processed by folding the two-plate stacked outer circumferential portion by 90° in a clockwise direction or a counterclockwise direction from an end of the two-plate stacked outer circumferential portion or a point closer to the center axis than the end of the two-plate stacked outer circumferential portion as a base point. a first process of forming, by performing a folding processing to an end portion of a material, a portion to be processed having a structure, in which a plurality of layers respectively having a thickness corresponding to a plate thickness of the material overlap each other, in the material such that a plate thickness direction of the layer is orthogonal to a plate thickness direction of the material; and a tooth forming process of changing, by performing a forging processing to the portion to be processed, a shape of the portion to be processed to a target shape while press-welding the layers of the portion to be processed to each other by plastic deformation, the method being characterized in that the first process includes: forming a first formed part having a cup bottom portion and an annular standing wall portion by folding an outer circumferential portion of the material by 90° into an L shape by drawing; forming a second formed part having a two-plate stacked outer circumferential portion by folding the standing wall portion by 90° so as to be overlapped on the cup bottom portion; and forming a third formed part (11C, 11D, 11E) having a two-plate stacked standing wall portion as the portion to be processed by folding the two-plate stacked outer circumferential portion by 90° in a clockwise direction or a counterclockwise direction from an end of the two-plate stacked outer circumferential portion or a point closer to the center axis than the end of the two-plate stacked outer circumferential portion as a base point. forming a first formed part having a cup bottom portion and an annular standing wall portion by folding an outer circumferential portion of the material by 90° into an L shape by drawing; forming a second formed part having a two-plate stacked outer circumferential portion by folding the standing wall portion by 90° so as to be overlapped on the cup bottom portion; and forming a third formed part (11C, 11D, 11E) having a two-plate stacked standing wall portion as the portion to be processed by folding the two-plate stacked outer circumferential portion by 90° in a clockwise direction or a counterclockwise direction from an end of the two-plate stacked outer circumferential portion or a point closer to the center axis than the end of the two-plate stacked outer circumferential portion as a base point.