To achieve continuously smooth operation of an electric power converter, without causing voltage discontinuity and to improve the efficiency of an electric vehicle drive system, when the electric power converter is transferred into a one pulse mode.

A controlling device of an electric vehicle is provided with an electric power converter, which drives an induction motor, calculating means 21dl to 21qm, which calculate each exciting current command Id and torque current command Iq for a speed fr, based on notch commands N from a master controller, and a means which emits PWM signals based on the result of the preceding calculations. In this controlling device, the exciting current constituent Id is maintained at a constant level at all times, irrespective of the notch commands above, and the torque current constituent Iq on the output of the maximum torque is made larger than the exciting current constituent Id by a given value, until the output voltage reaches the maximum potential voltage of the electric power converter. Also, the pulse mode of the output voltage is treated as one pulse, when the output voltage rises continuously in accordance with the speed of the induction motor and reaches the maximum voltage.