To smoothly perform the steering of a carrier truck by controlling the brake force of one drive wheel in accordance with the speed of the carrier truck.

When three traveling sensors 10A to 10C detect that a traveling path is curved, a control part 20 control both drive motors M1 and M2 so that smooth steering can be performed along a set traveling path. That is, a steering angle calculating part 40 recognizes a steering angle by calculating the difference between the revolving speeds of both motors M1 and M2 based on the difference of voltages of both tacho generators(TG) 32A and 32B, and the part 20 controls the revolving speeds of both motors M1 and M2 so that the steering angle may not exceed a fixed value. A power generation braking control parts 34A and 34B set the optimum resistance value so that the optimum brake force can be given to a drive motor to which conduction is cut off so that smooth steering can be performed along a traveling path at a currently traveling speed and makes a resistor of the resistance value consume voltage that is generated by the drive motor.