To reduce a Joule loss produced in a reactor installed in a booster converter.

In this hybrid automobile 10, a dc power from a battery 1 is converted into an alternating current by an inverter 2 after its voltage is increased by a booster converter 14 and then fed to a motor 3 and a liquid hydrogen tank 11 storing a liquid hydrogen as a fuel is mounted thereon. The booster converter 14 comprises the reactor 15 formed by fitting a coil 29 onto magnetic cores 27 and 28. The coil 29 of the reactor 15 is stored in a heat-insulated refrigerant container 23 and a refrigerant feed tube 21 feeding the liquid hydrogen H from the liquid hydrogen tank 11 is connected to the heat-insulated refrigerant container 23.