A three-phase AC to DC converter comprising: a three-phase rectifier bridge circuit that is configured to be connected to a three-phase AC power supply, and that includes rectifying devices which are connected in a bridge configuration between two DC buses; a three-phase full-bridge circuit that includes two serially-connected switching devices (3a-3f) for each of three phases, the two serially-connected switching devices (3a-3f) being connected between the DC buses at an output side of the three-phase rectifier bridge circuit, and that includes reverse blocking diodes (4a-4f) which are connected in parallel to the respective switching devices (3a-3f); a reactor that connects a connection point between the two serially-connected switching devices (3a-3f) of each phase to a corresponding phase of the three-phase AC power supply; a smoothing capacitor connected between the DC buses at an output side of the three-phase full-bridge circuit; DC voltage detection means that detects an output voltage between the DC buses; power supply phase detection means that detects a power supply phase of the three-phase AC power supply; and pulse width modulation means that outputs PWM signals which control the switching devices (3a-3f) wherein the pulse width modulation means outputs the PWM signals on the basis of the power supply phase and the output voltage; characterized in that the pulse width modulation means is configured to output, when only one phase of the three-phase AC power supply has a positive voltage, the PWM signals to switching devices (3a-3f) located at an upper arm side among the two serially-connected switching devices (3a-3f) that control the other two phases, and output, when only one phase of the three-phase AC power supply has a negative voltage, the PWM signals to switching devices (3a-3f) located at a lower arm side among the two serially-connected switching devices (3a-3f) that control the other two phases. a three-phase rectifier bridge circuit that is configured to be connected to a three-phase AC power supply, and that includes rectifying devices which are connected in a bridge configuration between two DC buses; a three-phase full-bridge circuit that includes two serially-connected switching devices (3a-3f) for each of three phases, the two serially-connected switching devices (3a-3f) being connected between the DC buses at an output side of the three-phase rectifier bridge circuit, and that includes reverse blocking diodes (4a-4f) which are connected in parallel to the respective switching devices (3a-3f); a reactor that connects a connection point between the two serially-connected switching devices (3a-3f) of each phase to a corresponding phase of the three-phase AC power supply; a smoothing capacitor connected between the DC buses at an output side of the three-phase full-bridge circuit; DC voltage detection means that detects an output voltage between the DC buses; power supply phase detection means that detects a power supply phase of the three-phase AC power supply; and pulse width modulation means that outputs PWM signals which control the switching devices (3a-3f) wherein the pulse width modulation means outputs the PWM signals on the basis of the power supply phase and the output voltage; characterized in that the pulse width modulation means is configured to output, when only one phase of the three-phase AC power supply has a positive voltage, the PWM signals to switching devices (3a-3f) located at an upper arm side among the two serially-connected switching devices (3a-3f) that control the other two phases, and output, when only one phase of the three-phase AC power supply has a negative voltage, the PWM signals to switching devices (3a-3f) located at a lower arm side among the two serially-connected switching devices (3a-3f) that control the other two phases.