A steering control device in which a steering portion including an
electric steering reaction force actuator and a steered portion including
an electric steered portion actuator are mechanically disconnectable and
connectable via a backup connection. Steer-by-wire control disconnects
the backup connection and uses control of the steered portion actuator to
set a steered angle corresponding to the steering condition and using
control of the steering reaction force actuator to add a steering
reaction force corresponding to the steered condition. Steering
assistance control connects the backup connection and adds a steering aid
force using at least one of the steering reaction force actuator and the
steered portion actuator. The power supply capacity of a steered vehicle
is selectively estimated and if the estimated power supply capacity
reaches a predetermined value or below during the steer-by-wire control,
steering is switched to the steering assistance control.