The object of the invention is to provide a less expensive active transmission control system for an automobile, capable of disconnecting an engine, without increasing the number of dog clutches.In an active shift transmission, a second intermediate shaft is provided between a transmission input shaft connected with an engine and a transmission output shaft, and the transmission ratio is determined by the product of gear ratios of two sets of transmission gears. Further, a differential gear box is connected between both intermediate shafts and a motor is connected to the third shaft of this differential gear box, so that the engine torque is borne by the motor on a temporary basis, whereby active transmission is performed. When the transmission gear of the input shaft is released, the engine rotation loss at the time of regenerative braking can be eliminated by disconnecting the engine.