An isolated power conversion apparatus having an isolation transformer characterized by comprising: a primary coil (n11, n12), a first secondary coil and one or a plurality of second secondary coil(s) that are provided for the isolation transformer; a first switching means disposed between a DC power supply and the primary coil (n11, n12), the first switching means driving the primary coil (n11, n12) in a forward direction; a second switching means disposed between the DC power supply and the primary coil (n11, n12), the second switching means driving the primary coil (n11, n12) in a reverse direction; a series circuit including a load and an inductor connected in series with each other, the series circuit being disposed on the first secondary coil side; a third switching means disposed in parallel with the series circuit, the third switching means being bidirectional; a fourth switching means disposed between the series circuit and the first secondary coil, the fourth switching means being bidirectional; a rectifying means and a smoothing means provided for each of the second secondary coil(s); and a control circuit driving each of the switching means, wherein the isolated power conversion apparatus is configured to send out power from the DC power supply toward the load as DC power or AC power of an arbitrary polarity, or regenerate and supply the DC power or AC power from the load to the DC power supply, each of the second secondary coil(s), the rectifying means and the smoothing means serve as an isolated DC power source, a circuit type on a primary side of the isolation transformer is a push-pull type, a half-bridge type or a full-bridge type; a circuit type on the first secondary coil side is a half-wave rectification type; wherein when the circuit type on the primary side of the isolation transformer is the half-bridge type, the DC power supply comprises a first DC power supply and a second DC power supply connected in series, one end of the primary coil (n11, n12) is connected to the poles of the DC power supply via the first switching means and the second switching means, respectively, and another end of the primary coil (n11, n12) is directly connected to a point between the first DC power supply and the second DC power supply; and when a duty ratio of a control signal for driving the first or second switching means changes, the control circuit drives the first switching means and the second switching means so that a sum of the duty ratio of the control signal for driving the first switching means and the duty ratio of the control signal for driving the second switching means is kept constant, so as to make an output voltage from each isolated DC source at a corresponding second secondary coil constant. a primary coil (n11, n12), a first secondary coil and one or a plurality of second secondary coil(s) that are provided for the isolation transformer; a first switching means disposed between a DC power supply and the primary coil (n11, n12), the first switching means driving the primary coil (n11, n12) in a forward direction; a second switching means disposed between the DC power supply and the primary coil (n11, n12), the second switching means driving the primary coil (n11, n12) in a reverse direction; a series circuit including a load and an inductor connected in series with each other, the series circuit being disposed on the first secondary coil side; a third switching means disposed in parallel with the series circuit, the third switching means being bidirectional; a fourth switching means disposed between the series circuit and the first secondary coil, the fourth switching means being bidirectional; a rectifying means and a smoothing means provided for each of the second secondary coil(s); and a control circuit driving each of the switching means, wherein the isolated power conversion apparatus is configured to send out power from the DC power supply toward the load as DC power or AC power of an arbitrary polarity, or regenerate and supply the DC power or AC power from the load to the DC power supply, each of the second secondary coil(s), the rectifying means and the smoothing means serve as an isolated DC power source, a circuit type on a primary side of the isolation transformer is a push-pull type, a half-bridge type or a full-bridge type; a circuit type on the first secondary coil side is a half-wave rectification type; wherein when the circuit type on the primary side of the isolation transformer is the half-bridge type, the DC power supply comprises a first DC power supply and a second DC power supply connected in series, one end of the primary coil (n11, n12) is connected to the poles of the DC power supply via the first switching means and the second switching means, respectively, and another end of the primary coil (n11, n12) is directly connected to a point between the first DC power supply and the second DC power supply; and when a duty ratio of a control signal for driving the first or second switching means changes, the control circuit drives the first switching means and the second switching means so that a sum of the duty ratio of the control signal for driving the first switching means and the duty ratio of the control signal for driving the second switching means is kept constant, so as to make an output voltage from each isolated DC source at a corresponding second secondary coil constant.