An automatic transmission includes a first planetary gear set, a second planetary gear set, and a first brake. A first sun gear includes a first split sun gear on a drive source side, and a second split sun gear on a side opposite to the drive source. The first spilt sun gear is coupled to the first brake, and is fixed to a transmission case during engagement of the first brake. The second split sun gear is constantly coupled to a second sun gear. An input shaft is constantly coupled to a first carrier while passing through the first split sun gear, and between the first and second split sun gears. An output shaft is constantly coupled to a second carrier.