Disclosed is an automatic transmission (10) in which, of four planetary gear sets (PG1, PG2, PG3, and PG4), two planetary gear sets (PG2, PG3) are arranged such that one of the two planetary gear sets (PG2, PG3) is disposed radially inward from the other to form a two-stage planetary gear set (PGt). One planetary gear set (PG1) of the other two planetary gear sets functions as a specified planetary gear set disposed adjacent to the two-stage planetary gear set in a transmission axial direction. A carrier (C3) of the radially outer planetary gear set (PG3) of the two-stage planetary gear set, a carrier (C1) of the specified planetary gear set, and an output section (an output gear (13)) are always engaged together.