A control apparatus controls a rotating machine including a stator having groups of phase windings, to control current application to the groups. The control apparatus includes power converters converting received power to AC power and supplying the AC power to the rotating machine, a harmonic component cancellation section reducing a harmonic component superimposed on a fundamental wave component by a cancellation process in an estimated-rotating coordinate system for at least one of voltage and current of each system, when a unit of a group of components controlling current application to a specific group of the windings is defined as a system, an induced voltage estimation section estimating an induced voltage based on information common to the systems including a voltage value and a current value calculated by the cancellation process, and a magnetic-pole-position estimation section estimating a magnetic pole position of a rotor based on the estimated induced voltage.