A power conversion apparatus including a three-phase transformer having at least four three-phase windings, and three converter arms each configured by connecting one or plural unit converters each including a switching device and an energy storage element in series. A power source or a load is connected to a first three-phase winding of the transformer, three series circuits which connects second and third three-phase windings of the transformer, and the converter arms in series with each other are connected in parallel, the parallel connection point is a DC terminal, and a magnitude relationship between a coupling coefficient of the first and second three-phase windings, and a coupling coefficient of the first three- and third three-phase windings is equal to a magnitude relationship between a coupling coefficient of the fourth and second three-phase windings, and a coupling coefficient of the fourth and the third three-phase windings.