An automatic transmission, which establishes automatic shifts in a multiple gear stages by selectively inputting a plurality of input rotations to a planetary gear set (G), comprises first (C1) and third (C3) clutches connected through a reduction planetary gear set (G1) to an input shaft (11) and transmitting a decelerated rotation to the planetary gear set (G) and a second clutch (C2) directly connected to the input shaft (11) and transmitting a non-decelerated rotation to the planetary gear set (G). The reduction planetary gear set (G1) is arranged on the end of a boss portion of a transmission case wall (10) and the one element (S1) is fixed to the end of the boss portion, hydraulic servos of the first and third clutches (C1,C3) are arranged on the boss portion, a hydraulic servo of a second clutch (C2) is arranged in the other side of the reduction planetary gear set (G1) from the hydraulic servos, and hydraulic paths for the hydraulic servos are formed in the boss portion.