IN-VEHICLE POWER SUPPLY DEVICE

An in-vehicle power supply device includes a first voltage conversion unit for performing at least a step-down operation to lower a voltage applied to a first conductive path electrically connected to an in-vehicle power storage unit, and apply the lowered voltage to a second conductive path; a second voltage conversion unit for performing at least the step-down operation to lower a voltage applied to a first conductive path and apply the lowered voltage to a second conductive path, a second voltage conversion unit having a smaller power capacity than the first voltage conversion unit; a driving unit that drives the first voltage conversion unit and the second voltage conversion unit, and a capacitor that is electrically connected to the second conductive path and is charged with a current flowing through the second conductive path.