A power conversion device in an embodiment includes a first power converter; a plurality of direct current-direct current (DCDC) converter devices; and a second power converter. The first power converter includes a plurality of first positive-side arms; a plurality of first negative-side arms; a first positive-side star connection line configured to connect the plurality of first positive-side arms in a star shape; a first negative-side star connection line configured to connect the plurality of first negative-side arms in a star shape; and a first terminal configured to connect the first positive-side star connection line and the first negative-side star connection line to each phase of a power supply side alternating current (AC) system and the plurality of first positive-side arms and the plurality of first negative-side arms mutually convert a first AC power and a first DC power of the power supply side AC system. A plurality of DCDC converter devices mutually convert the first DC power and the second DC power. The second power converter includes a plurality of second positive-side arms; a plurality of second negative-side arms; a second positive-side star connection line configured to connect the plurality of second positive-side arms in a star shape; a second negative-side star connection line configured to connect the plurality of second negative-side arms in a star shape; and a second terminal configured to connect the second positive-side star connection line and the second negative-side star connection line to each phase of a load-side AC system, and the plurality of second positive-side arms and the plurality of second negative-side arms mutually convert the second DC power and the second AC power.