To provide a power conversion device that effectively reduces common mode components caused by other stray capacitances even if stray capacitances between midpoints of switching arms and a ground line are not main paths of high frequency leakage currents.

In a power conversion system having a first power conversion device in which a plurality of lines of switching arms each comprising a series connection of two arms each comprising one or more switching elements are connected in parallel and an AC power supply is connected between respective midpoints of at least two lines of switching arms, and a second power conversion device which converts power from a power storage device to feed both ends of the switching arms, the plurality of lines of switching arms include a switching arm having a relatively low impedance connected to the midpoint, the second power conversion device comprises at least one switching element, and a control circuit for controlling the switching element of the second power conversion device is connected via an insulated circuit.