are performed at step 112 in accordance with the equation 2 the motor b speed u03c9b is controlled in such a manner that the engine speed u03c9e becomes zero while the vehicular speed u03c9v is kept constant at step 113 the vehicle drive torque u03c4v is controlled by controlling the motor a torque u03c4a at this time the torque control is performed in such a manner that with u03c4e 0 in the equation 3 the vehicle drive torque u03c4v is determined in accordance with the equations 4 5 and 6 from the equation 11 to satisfy the relationship of u03c4v gt 0 the vehicle is usually driven in such a manner that the motor a is in the power running state and the motor b is in the power generating state of course at step 114 an operation for continuously stopping the control of the engine is performed in the case of the first speed mode an operation for controlling the motor a speed u03c9a into zero is performed at step 115 and an operation for stopping the control of the motor b is performed at step 116 with these operations the motor a is turned into an electrically locked state and the motor b is turned into a free run state and thereby the planetary gear a4 having the large gear ratio between the input side and the output side is driven by the engine 1 in a state in which the sun gear 4s of the planetary gear a4 is fixed that is to say the speed change ratio in the first speed mode is equivalent to a low gear ratio of a usual manual transmission and.