Abstract: An electric power supply apparatus includes a first power supply that supplies electric power to a first control device configured to control a vehicle, a second power supply that supplies electric power to a second control device configured to control the vehicle, a starter switch configured to be operated by an occupant, and an activation control unit that starts or stops the vehicle based on a change in voltage of the starter switch that occurs when the starter switch is operated, wherein the starter switch is in a state of being connected to the first power supply and the second power supply, and when the starter switch is operated, electric power is supplied to the starter switch from at least one of the first power supply and the second power supply.