A controller of a multiphase rotating electric machine has two inverters outputting an alternating current to two sets of windings, and a control section driving a motor by switching between a “two-system driving mode” supplying power from the two inverters to the two sets of winding and a “one-system driving mode” supplying power from one of the two inverters to the corresponding set of windings, The control section in the one-system driving mode changes at least one of a maximum amplitude and a current phase of the alternating current used in the two-system driving mode to compensate for a reluctance torque generated by a mutual inductance of the two sets of winding in the two-system driving mode.