A control device obtains a post-code extension steering torque by performing moving average processing of weighting an oversampling signal obtained by oversampling processing, obtains a base assist torque based on the post-code extension steering torque signal, acquires a base assist torque signal that decreases the base assist torque as a vehicle speed increases, performs stabilization processing on the base assist torque signal to obtain an assist torque signal according to the assist torque of an electric power steering device.