A power supply control system for a vehicle includes a supply line system, a first electric generating means, a second electric generating means, and a control means. The first electric generating means generates electricity through use of a mechanical drive force of a drive source of the vehicle, which drives the vehicle to run. The second electric generating means generates electricity through use of a heat energy. The first and second electric generating means are connected to the supply line system. The control means controls the first electric generating means and the second electric generating means.