An automatic transmission having a construction in which a third planetary gear mechanism is arranged in parallel with CR-CR coupled first and second planetary gear mechanisms so that the drive force is transmitted from the carrier of the first planetary gear mechanism to the ring gear of the third planetary gear mechanism. The input is transmitted to a first sun gear through a first clutch and to a second sun gear through a second clutch. The construction further includes a one-way clutch for fixing the sun gear of the third planetary gear mechanism.
