A power-semiconductor element driving circuit for driving a power semiconductor element (lower arm 32u), comprising: - a positive-voltage power supply (second DC power supply 61) for supplying, between a control terminal and a reference terminal in the power semiconductor element, a positive bias voltage; - a negative-voltage power supply (third DC power supply 62) for supplying, between the control terminal and the reference terminal in the power semiconductor element, a negative bias voltage, a positive side of which is connected to a negative side of said positive-voltage power supply; - a gate driving circuit that is adapted to supply, based on a control signal of a control circuit (motor-drive control circuit 4), either the positive bias voltage for turning on the power semiconductor element or the negative bias voltage for turning off the power semiconductor element, between the control terminal and the reference terminal in the power semiconductor element; and - a voltage detector (voltage detection circuit 37, light emitting diode 41) that is adapted to detect a detection target voltage that is a sum voltage of the positive bias voltage and the negative bias voltage; the power-semiconductor element driving circuit being characterized in that it further comprises - a switching element (transistor 81, photo-MOSFET 42) whose one terminal is connected to the control terminal of the power semiconductor element and whose another terminal is connected to a negative side of the negative-voltage power supply and which is off when the value of the detection target voltage is equal to or higher than a voltage setting value; wherein, when a value of the detection target voltage becomes lower than the voltage setting value or when a voltage between the control terminal and the reference terminal in the power semiconductor element increases in a state where the value of the detection target voltage is lower than the voltage setting value, the voltage detector (37, 41) is adapted to turn on the switching element (81, 42) to thereby supply, between the control terminal and the reference terminal in the power semiconductor element, a negative bias voltage from the negative-voltage power supply. - a positive-voltage power supply (second DC power supply 61) for supplying, between a control terminal and a reference terminal in the power semiconductor element, a positive bias voltage; - a negative-voltage power supply (third DC power supply 62) for supplying, between the control terminal and the reference terminal in the power semiconductor element, a negative bias voltage, a positive side of which is connected to a negative side of said positive-voltage power supply; - a gate driving circuit that is adapted to supply, based on a control signal of a control circuit (motor-drive control circuit 4), either the positive bias voltage for turning on the power semiconductor element or the negative bias voltage for turning off the power semiconductor element, between the control terminal and the reference terminal in the power semiconductor element; and - a voltage detector (voltage detection circuit 37, light emitting diode 41) that is adapted to detect a detection target voltage that is a sum voltage of the positive bias voltage and the negative bias voltage; the power-semiconductor element driving circuit being characterized in that it further comprises - a switching element (transistor 81, photo-MOSFET 42) whose one terminal is connected to the control terminal of the power semiconductor element and whose another terminal is connected to a negative side of the negative-voltage power supply and which is off when the value of the detection target voltage is equal to or higher than a voltage setting value; wherein, when a value of the detection target voltage becomes lower than the voltage setting value or when a voltage between the control terminal and the reference terminal in the power semiconductor element increases in a state where the value of the detection target voltage is lower than the voltage setting value, the voltage detector (37, 41) is adapted to turn on the switching element (81, 42) to thereby supply, between the control terminal and the reference terminal in the power semiconductor element, a negative bias voltage from the negative-voltage power supply.