PURPOSE: To improve the comfortability of a vehicle to ride on, and to prevent the slipping of wheels thereof, by using a solid-state circuit breaker and thereby making the rise of a power regenerative braking force earlier than the rise of air braking force.

CONSTITUTION: When power running is conducted, a circuit breaker 2 is closed, while the respective solid-state circuit breakers P of solid-state circuit breaker arms 13a and 13b are struck, and a speed control is performed by chopper control devices 10a and 10b. When a coasting operation is conducted, the arc of the solid-state circuit breakers P are extinguished so as to prevent the occurrence of a phenomenon of backing breaking due to a circulating current of the parallel circuit of two motors. When power regenerative braking is conducted, the circuit breaker 2 is closed, while the respective solid-state circuit breakers B of the solid-state circuit breaker arms 13a and 13b are struck, and the speed control is performed by the chopper control devices 10a and 10b. Also after the completion of the power regenerative braking, the solid-state circuit breakers B are extinguished to prevent the occurrence of the phenomenon of the backing braking.