PURPOSE: To shorten an axial directional length of a transmission by respectively connecting the fellow first/second cylinder gears and the fellow first/second carriers, also connecting the second carrier and the third ring gear, in a planetary gear type transmission provided with three sets of planetary gear trains.

CONSTITUTION: A double pinion type planetary gear train G1, constituted of respectively sun gears S1 to S3, carriers C1 to C3 and ring gears R1 to R3, and single pinion type planetary gear trains G2, G3 are parallelly arranged on the same axis, to connect the sun gear S1 engageably/disengageably to an input shaft 11 through a clutch K1. The carriers C1, C2 and the ring gear R3 are connected, to connect these carrier and gear to the input shaft 11 engageably/disengageably through a clutch K2. The ring gears R1, R2 are connected, also to connect the sun gears S2, S3, and these ring gear and sun gear are connected to the input shaft 11 engageably/disengageably through a clutch K3, to directly connect the carrier C3 to an output shaft 12.