To prevent efficiency reduction in a motor, and to more accurately control the target speed of a vehicle by correcting a reference power so that the speed of the vehicle approaches the target speed, and by controlling power supplied to the motor for running based on the corrected power.

A means 12 for inputting a target good speed inputs the target speed of a vehicle to a means 18 for calculating a reference power, and the means 18 for calculating the reference power calculates the reference power to be supplied to a motor required for allowing the vehicle to run at the target speed. Then, the target speed is compared with the speed of the vehicle being detected by a vehicle-speed sensor 10 by using a means for setting a correction coefficient, the correction coefficient when the speed of the vehicle is lower than the target speed is set larger than that when the speed of the vehicle is set higher than the target speed, and the reference voltage is corrected based on the set correction coefficient by a means 19 for correcting supply power so that the speed of the vehicle approaches the target speed. Based on the corrected power, power supplied to a motor 22 for running is controlled by power controlling.