A charging control system that controls charging of a plurality of vehicles that run on electricity includes: an assignment unit that assigns an order of priority relating to charging to the plurality of vehicles based on a predetermined index; a receiving unit that receives electric power demands that are requested from an electric power supply side; and a control unit that selects from among the plurality of vehicles in the order of highest priority charging-object vehicles in which the ON/OFF setting for turning charging ON and OFF is to be set to ON, and sets the ON/OFF setting of charging-object vehicles to the ON setting. The control unit changes the number of charging-object vehicles in response to changes in electric power demands over time.