VEHICLE POWER SUPPLY SYSTEM

A vehicle power supply system for supplying electric power to a load mounted on a vehicle, comprising: a main power supply source; a sub-power supply source; a main power distribution control unit for distributing and supplying electric power of the main power supply source to a plurality of first loads; and a sub-power distribution control unit for distributing and supplying electric power of the sub-power supply source to the plurality of second loads and being connected to the main power distribution control unit so as to be capable of supplying electric power of the sub-power supply source via a switch, wherein when the switch is in a first state capable of supplying electric power from the sub-power supply source to the plurality of second loads, the switch is controlled to a cut-off state.