Vehicle Power Supply Device

A vehicle power supply device comprises: a first power storage element group having multiple power storage elements connected in series; a second power storage element group connected in series to the positive pole side of the first power storage element group forming a high-voltage DC power supply by being combined with the first power storage element group; an active balancer; a first switching means and second switching means disposed between the first power storage element group and a low-voltage load; a control means; an interrupting means for interrupting power from the high voltage DC power supply; and a power leakage detection means. The control means determines a signal transmitted from the power leakage detection means during a dead time period in which the first and second switching means are OFF, and interrupts power supplied to the load for a prescribed period if the leakage current has reached a prescribed level.