PURPOSE: To avoid application of overload to a running motor effectively at the time of climbing a hill, while suppressing power consumption, even when the motor speed is controlled by open loop system depending on the stepping amount of accelerator pedal.

CONSTITUTION: The speed command correcting section 15 in a motor control circuit 11 sets a motor rotation command frequency (fo) with reference to a map using an accelerator pedal stroke (tod and the slope of road detected at a road slope operating section 14 as parameters. The map stores values for setting a lower motor rotation command frequency (f) as the slope of road increases. Consequently, the speed of a running motor 5 is corrected to decrease as the slope of road, and thereby the climbing resistance, increases even if the accelerator pedal stroke (fo) is constant and thereby the torque is increased relatively thus avoiding overload of the running motor. Since overload of motor is avoided, consumption of a battery 9 is suppressed.