In an abnormality determination system, when a drive signal is input and no shutdown signal for stopping gate drive of switching elements is input, a signal switching section outputs the drive signal to a bridge circuit. When a shutdown signal is input, the signal switching section stops output of the drive signal and activates a shutdown function of an inverter. An abnormality determination section determines an abnormality in the shutdown function. When a power source relay is opened, a control unit drives the bridge circuit to start a discharge process of discharging electric charge from a smoothing capacitor, and activates the shutdown function during execution of the discharge process. When it is determined that a directly or indirectly detected voltage of the smoothing capacitor has dropped during operation of the shutdown function, the abnormality determination section determines that the shutdown function is abnormal.