There is provided a control system for an electric motor to which electric power is supplied from a DC power supply via a multi-phase inverter, the multi-phase inverter including switch units respectively provided on a positive side and a negative side of arms corresponding to respective phases, each switch unit including a switching element and a reflux diode connected in parallel thereto. The control system comprises a phase current detection unit for detecting phase currents which flow between the inverter and the electric motor, a DC component acquiring unit for acquiring DC components of the respective phase currents, and a short-circuiting determination unit for determining that a short-circuit failure occurs in the inverter when at least one of the DC components of the phase currents acquired by the DC component acquiring unit exceeds a threshold. Consequently, the short-circuit failure of the inverter can be detected even though the control of the electric motor is stopped.