A power supply control apparatus includes: a first system configured to supply electric power of a first power supply to a first load; a second system configured to supply electric power of a second power supply to a second load; an inter-system switch capable of connecting the first system to the second system and disconnecting the first system from the second system; a battery switch capable of connecting the second power supply to the second system and disconnecting the second power supply from the second system; a primary ground fault detection unit configured to cut off the inter-system switch and conduct the battery switch when a ground fault of the first system or the second system is detected by the primary ground fault detection unit; a secondary ground fault detection unit as defined herein; and a failure determination unit as defined herein.