A power supply control device for controlling power supply to a load of a vehicle using a first battery and a second battery, the power supply control device comprising: an acquisition unit that acquires a power supply state of the vehicle; a diagnostic unit that performs diagnosis of the second battery when the power supply state of the vehicle is switched from off to on; and a control unit that controls an electrical connection state between the load and the second battery, wherein the control unit controls the first state in which power can be supplied from the second battery to the load when the diagnosis unit diagnoses that the second battery is normal.