An automatic transmission is provided comprising a transmission case, a first shaft housed in and rotationally supported by said transmission case, and capable of receiving torque from an engine, a first shifting gear mechanism arranged coaxially with the first shaft, and a second shifting gear mechanism including a second planetary gear set. The second planetary gear set is housed within the transmission case and arranged coaxially with the first shaft, one of its sun and ring gears is capable of rotating together with the input shaft, and the other of the sun and ring gears is fixed to the transmission case. The automatic transmission further comprises first and second frictional elements arranged at least partly overlapped with the second planetary gear set in the axial direction between the planetary gear set and the transmission case in the radial direction. Accordingly, the plurality of frictional elements may be arranged on a shorter shaft without excessively increasing the radial size of the automatic transmission.