A control unit for a rotary electric machine includes a first current command module, a second current command module, a change module, and a return module. The first module performs a first current command on a maximum efficiency characteristic line on a d-q plane thereby to drive the machine at a maximum efficiency. The second module performs a second current command on a switching line set at a retard angle side relative to the maximum efficiency characteristic line. The change module changes a control mode from a rectangular wave voltage phase control mode to an overmodulation current control mode when an operation point of the machine reaches the switching line. The return module returns the current command from the second command to the first command after performance of the second command for a predetermined period.