A circuit breaker device for use on an electric vehicle has a high-voltage drive power supply for supplying electric energy to a load to drive the electric vehicle, a circuit breaker for cutting off the electric energy supplied from the drive power supply to the load, a sensor assembly for detecting conditions of the electric vehicle, and a controller for controlling operation of the circuit breaker in response to a detected signal from the sensor assembly. The controller is connected to a low-voltage accessory power supply for energizing accessories on the electric vehicle, and also connected to the drive power supply through a power supply converter for converting the electric energy supplied from the drive power supply, so that the controller can be energized at all times by at least one of either the accessory power supply or the drive power supply. The circuit breaker has first and second shunt coils energizable for cutting off the output of the electric energy from the drive power supply and the accessory power supply, the first shunt coil being connected to the drive power supply and the second shunt coil being connected to the accessory power supply.