To prevent the occurrence of engagement error without needing a post-working, such as cutting-work, etc., when a ring-gear in the outer-circumferential part is formed with rolling-formation in order to reduce the manufacturing cost, etc.

Since an engagement tooth 16 of the ring-gear 12 of a driving plate 10 for vehicle, is provided with a projecting arch surface 50 having about 0.70 mm radius in the rear-side corner part of the front surface side edge surface 40, a pinion 30 is quickly engaged with the ring-gear 12 without causing the engagement error. In this case, the above projecting arch surface 50 is simultaneously roll-formed when the front surface side end surface 40, front-side tooth surface 42 and rear-side tooth surface 44, are integrally roll-formed with a die 74 with tooth, and therefore, the driving plate 10 for vehicle is simply manufactured at a low cost and also, the yield is improved and the manufacturing cost is decreased because of dispensing with the post-working, such as the cutting-work for forming the pin corner, the burr-removal, etc.