An object of the present invention is to reduce an overcurrent of an inverter and a motor. A control device for an electric motor in which windings of respective phases are independently connected, the control device for the electric motor uses a zero-phase current calculation means for calculating a zero-phase current based on detection values of currents of the respective phases flowing in the electric motor and a position of a rotor of the electric motor to control a current flowing in the electric motor such that a vector sum of a drive current and the zero-phase current is equal to or lower than a predetermined current.