There are provided the control device for an AC rotating machine, and the AC rotating machine drive system and an electric power steering system including the control device for an AC rotating machine, which are capable of supplying high-frequency powers, on which high-frequency components corresponding to high-frequency signals input thereto are superimposed, to the AC rotating machine, and calculating a rotational position of the AC rotating machine based on a phase difference between an output torque high frequency contained in an output torque of the AC rotating machine and the high-frequency signals to estimate the rotational position of the AC rotating machine without being constrained by a rotational speed of the AC rotating machine, whether or not the AC rotating machine is electrically salient, and whether or not magnetic saturation has occurred.