Electric power conversion device has first and second operation modes. First operation mode is of converting DC power from a first terminal into DC power having a desired voltage to be output to second terminal. Second operation mode is of converting DC power from the second terminal into DC power having a desired voltage to be output to first terminal. Switching section is configured to, in first operation mode, be turned on to cause short-circuiting between both ends of capacitor of rectifying circuit, and, in second operation mode, be turned off. First conversion part is configured to, in first operation mode, supply DC power-from first terminal, from first winding to second conversion part through a conversion circuit, and, in second operation mode, output to first terminal a voltage obtained by adding an output voltage of rectifying circuit to an output voltage of conversion circuit.