A DC/DC converter is able to step down a voltage value of a high-voltage battery, and is able to step up a voltage value of a low-voltage battery. The low-voltage battery is a battery that provides a lower voltage value than the high-voltage battery. The DC/DC converter includes a transformer, a third diode and a reactor. The transformer includes a first coil and a second coil. The first coil is connected to the low-voltage battery. The second coil is connected to the high-voltage battery. An anode of the third diode is connected to one end of the first coil. One end of the reactor is connected to a cathode of the third diode, and the other end of the reactor is connected to a positive electrode terminal of the low-voltage battery.