A control apparatus controlling a rotating machine includes a signal output unit that outputs an excitation signal to a resolver used for detecting a rotational angle of the rotating machine; a demodulation unit that demodulate a signal related to the rotational angle based on a detection of a modulated signal and the excitation signal so as to output a demodulated signal; a filter that eliminates higher harmonics in the demodulated signal outputted by the demodulation unit so as to output a calculated angle of the rotational angle; and an operating unit that controls a switching element included in a DC-AC conversion circuit to be ON and OFF based on the calculated angle of the rotational angle outputted by the filter, so as to control the rotating machine with an output voltage of the DC-AC conversion circuit supplied to the rotating machine.