The control apparatus for an electric rotating machine includes a prediction section to predict a controlled variable of the electric rotating machine applied with an output voltage of a power conversion circuit for each of prescribed operation states of the power conversion circuit, and a manipulation section to manipulate the power conversion circuit to operate in one of the respective operation states determined as an actual operation state based on the controlled variable predicted by the prediction section. The control apparatus further includes an average voltage direction calculating section to calculate a direction of an average output voltage vector of the power conversion circuit. The manipulation section includes a priority setting section to set priority for each of the operation states based on the direction of the average output voltage vector calculated by the average voltage direction calculating section in determining the actual operation state.