When a vehicle, for example, a passenger vehicle stops, electric power is supplied to a passenger compartment mechanism and/or an entertainment device from a power supply isolated from the device relating to a vehicle travel system. Electric power consumption is managed to secure the electric power necessary to create a travel start possible state. Further, a key position is provided to supply electric power only to the passenger compartment mechanism and/or the entertainment device. With this arrangement, music and the like can be comfortably enjoyed by stopping the vehicle.