A controller for a multiple-phase rotating machine includes power converters for supplying alternating current to winding sets of the rotating machine. A pair of each electrical power converter and a corresponding winding set forms a system. The controller further includes a failure detector for detecting a failure in each system. The failure causes a braking current in the rotating machine. The controller further includes a control section for setting a d-axis current and a q-axis current to drive the power converter in each system. When the failure detector detects the failure in any one of the systems, the control section stops the power converter in the failed system and sets the d-axis current in the normal system in such a manner that an electric current in the failed system is reduced.