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.