PURPOSE: To prevent the slip by supplying the electric vehicle with currents lower than an accelerating current value before the slip when the slip is generated.

CONSTITUTION: An information transmitter 28 transmits a speed command from a master controller 281 and a command of a fixed current value from a current command device 282 to a ground electric power substation 21 through an on-car antenna 29. A stringing 23x is supplied with the power of voltage and currents corresponding to the commands given from the ground electric power substation 21. When either of wheels coupled with four main motors 5 occurs a slip, a slip detector 50 is operated, a contact 50A is opened, and the excitation of a control coil 51A for a breaker 51 is interrupted. In this case, a motorman returns the master controller 281 to a noncommand position once, drops the current value of the current command device 282 when there is a danger that the wheel is slipped again, and operates the master controller 281 to issue the speed command.