A power conversion device includes a transformer, and a first bridge circuit connected to a primary-side of the transformer and capable of switching a polarity of a connection between a pair of DC bus bars on the primary-side and the transformer. A second bridge circuit is connected to a secondary-side of the transformer and capable of switching a polarity of a connection between a pair of DC bus bars on the secondary-side and the transformer. A control device is provided which is capable of performing control of switching the first bridge circuit and the second bridge circuit with a phase difference. The control device has a frequency adjustment unit for adjusting a frequency of switching of the first bridge circuit and the second bridge circuit, according to an output from the first bridge circuit or the second bridge circuit and a target value.