VEHICLE POWER SUPPLY DEVICE

A vehicle power supply device includes a voltage decrease circuit, a control unit, and a voltage increase power supply unit. The voltage decrease circuit includes multiple MOSFETs as switching elements, receives a voltage supplied from a battery, decreases, by turning on and turning off the switching elements, the received voltage to an operation voltage of an operation target device, and outputs the decreased voltage to the operation target device. The control unit controls an operation of the voltage decrease circuit. The voltage increase power supply unit is connected with the voltage decrease circuit in parallel, receives the voltage supplied from the battery, increases the received voltage, and outputs the increased voltage to the control unit.