An electric power converter comprising: a control unit configured to output a PWM signal; a bridge circuit configured to produce AC electric power to be supplied to a motor by making semiconductor switching devices turned-on and -off by the PWM signal; a cut off unit provided between the control unit and the bridge circuit for cutting off the PWM signal supplied to the bridge circuit from the control unit by a gate signal; and a monitoring unit configured to generate a test signal for checking the cut off unit, characterized in that the cut off unit comprises: a switching circuit configured to switch between the test signal and an external cut off signal to output one of the test signal and the external cut off signal; a delay circuit configured to have the output signal of the switching circuit inputted and configured to allow the output signal to pass through the delay circuit only after a preset time has elapsed from the time at which the output signal is changed; and means for outputting the signal inputted to the delay circuit to the monitoring unit as a feedback signal, the monitoring unit being configured to output a test signal with a duration being shorter than a delay time, so that no PWM signal is cut off by the test signal, as being the preset time to make a decision as to whether the feedback signal outputted from the cut off unit is in agreement with the test signal and, when the feedback signal and the test signal are in disagreement with each other, to make a decision that a state is abnormal. a control unit configured to output a PWM signal; a bridge circuit configured to produce AC electric power to be supplied to a motor by making semiconductor switching devices turned-on and -off by the PWM signal; a cut off unit provided between the control unit and the bridge circuit for cutting off the PWM signal supplied to the bridge circuit from the control unit by a gate signal; and a monitoring unit configured to generate a test signal for checking the cut off unit, characterized in that the cut off unit comprises: a switching circuit configured to switch between the test signal and an external cut off signal to output one of the test signal and the external cut off signal; a delay circuit configured to have the output signal of the switching circuit inputted and configured to allow the output signal to pass through the delay circuit only after a preset time has elapsed from the time at which the output signal is changed; and means for outputting the signal inputted to the delay circuit to the monitoring unit as a feedback signal, a switching circuit configured to switch between the test signal and an external cut off signal to output one of the test signal and the external cut off signal; a delay circuit configured to have the output signal of the switching circuit inputted and configured to allow the output signal to pass through the delay circuit only after a preset time has elapsed from the time at which the output signal is changed; and means for outputting the signal inputted to the delay circuit to the monitoring unit as a feedback signal, the monitoring unit being configured to output a test signal with a duration being shorter than a delay time, so that no PWM signal is cut off by the test signal, as being the preset time to make a decision as to whether the feedback signal outputted from the cut off unit is in agreement with the test signal and, when the feedback signal and the test signal are in disagreement with each other, to make a decision that a state is abnormal.