An automatic transmission comprises a reduction planetary gear, two clutches transmitting a decelerated rotation transmitted from the reduction planetary gear, and a planetary gear set comprising two elements to which the decelerated rotation is inputted through the two clutches. The reduction planetary gear and the two clutches are arranged in one side of the planetary gear set. The second clutch is closer to the planetary gear set than the clutch. The input side member of the first clutch is connected to an output element of the reduction planetary gear and the input side member of the second clutch. The output side member of the first clutch is extended through the radial inner space of the second clutch and connected to one of the two elements of the planetary gear set. Thus, no member is arranged in the radial outer side of the both clutches, and the both clutches are radially enlarged.