PURPOSE: To improve speed change responsiveness by arranging two counter shafts in parallel to an input shaft through a counter shaft selecting clutch and meshing a gear, selected by a gear selecting clutch on each counter shaft, with the gear of an output shaft.

CONSTITUTION: Drive torque, input through a torque converter 5 from an engine, is selectively transmitted to counter shafts 3, 4 from an input shaft 1 through gears 37, 35, 36 and counter shaft selecting clutches 6, 7. A forward 1-speed gear, 2-speed gear 9, pinion, reverse 1-speed gear 10 and a 2-speed gear 11, selected by gear selecting clutches 14, 15, are deceleration-transmitted to a gear 13 of an output shaft 2 partly through idle gears 38, 39. Thus improving speed change responsiveness, drive power is transmitted without interruption not only between the first and second speeds but also between the forward and reverse, and work efficiency can be substantially improved.